The Truth About Lying Essay Summary Of An Article
Judging by the reactions of critics at screenings, the film has struck a nerve. “Any era is a good one for liars, but folks on every point of the moral or political spectrum are likely to agree: We are living in a fibbers’ renaissance,” Dennis Harvey wrote in Variety. “As Yael Melamede’s documentary notes, various bendings of the truth have among other things recently led us into war, crashed the economy, and allowed potentially catastrophic despoiling of the planet to continue more or less unchecked.”
Indeed, the film was prompted in part by the misdeeds of the mortgage crisis, and it turned out to be all too timely. Two days after it was completed, news broke about the NBC News anchor Brian Williams embellishing a tale about a helicopter journey in Iraq. Then last month, 11 educators were convicted of racketeering and other charges for their roles in Atlanta’s standardized test cheating case.
The film includes interviews with Marilee Jones, the former dean of admissions at the Massachusetts Institute of Technology, who lied about her academic credentials; Joe Papp, a former professional cyclist who pleaded guilty to distributing performance-enhancing drugs; and Kelley Williams Bolar, an Ohio mother who lied about her home address so her daughters could attend school in a better district.
“We avoided extremes — we didn’t do the Madoffs of the world and stories of incredible poverty,” Ms. Melamede said. “We thought the bigger takeaway is people who are more like us, not psychopathic and not desperate.”
In seeking out interview subjects, the filmmakers found that rather than wanting to conceal their misdeeds, people were eager to confess — even on camera. To some extent, they had nothing to lose. “Most of them had been so shamed publicly,” said Ms. Melamede, a producer of documentaries (including the Academy Award-winning short “Inocente” and the Academy Award-nominated “My Architect”) who is making her directing debut.
But in the cases of the more prominent transgressors, they also wanted to relate their experiences in their own words, because until now the news media had done it for them.
“By sharing stories, we’re reminded of our better selves,” Ms. Melamede said.
The film also shows Professor Ariely’s research experiments, including one in which subjects were asked to take a math test they could not possibly finish in the allotted time and then score themselves. No fewer than 70 percent exaggerated the results. But when people had to list the Ten Commandments or swear on a Bible — even if they were atheists — beforehand, they reported their scores more honestly.
“Just thinking about good behavior reduces cheating,” Ms. Melamede said.
The process of making the film revealed clear patterns about how people lie, the filmmakers said, namely that people find ways to justify their behavior.
“You can see the process of rationalization across the movie — every story is a story of rationalization,” Professor Ariely said. “There’s the rationalization of doing something for other people, there’s the rationalization that nobody else would suffer, the rationalization that everybody else was doing it.
“We are really good at this,” he added. “If you had to pick a good human skill, rationalization is one of them. We’re so fantastic at it.”
The filmmakers want the movie to have a lasting, consciousness-raising effect, to make people continue to think about their own honesty. As a result, the film is part of a larger “(Dis)Honesty Project” that includes a middle and high school curriculum (the hope is to run a pilot program with two or three schools in the fall); ethics training for corporations; and a “truth box” that invites people to step inside and be recorded on video telling the truth about a lie (it has so far been set up in New York City and Charlottesville, Va.).
Ms. Melamede said that making the film had heightened her own awareness about lying and made her more empathetic with those who go too far.
“But for the grace of something, we could all be in those situations,” she said. “I think I could be so many of these people.”Continue reading the main story
Lying and truth-telling
Lying is probably one of the most common wrong acts that we carry out (one researcher has said 'lying is an unavoidable part of human nature'), so it's worth spending time thinking about it.
Most people would say that lying is always wrong, except when there's a good reason for it - which means that it's not always wrong!
But even people who think lying is always wrong have a problem... Consider the case where telling a lie would mean that 10 other lies would not be told. If 10 lies are worse than 1 lie then it would seem to be a good thing to tell the first lie, but if lying is always wrong then it's wrong to tell the first lie...
Nobody who writes about lying nowadays can do so without acknowledging an enormous debt to this groundbreaking book: Lying: Moral choice in public and private life, by Sisela Bok, 1978.
What is a lie?
Lying is a form of deception, but not all forms of deception are lies.
Lying is giving some information while believing it to be untrue, intending to deceive by doing so.
A lie has three essential features:
- A lie communicates some information
- The liar intends to deceive or mislead
- The liar believes that what they are 'saying' is not true
There are some features that people think are part of lying but aren't actually necessary:
- A lie does not have to give false information
- A lies does not have to be told with a bad (malicious) intention - white lies are an example of lies told with a good intention
This definition says that what makes a lie a lie is that the liar intends to deceive (or at least to mislead) the person they are lying to. It says nothing about whether the information given is true or false.
This definition covers ordinary cases of lying and these two odd cases as well:
- the case where someone inadvertently gives true information while believing that they're telling a lie
- I want the last helping of pie for myself, so I lie to you that there is a worm in it. When I later eat that piece of pie I discover that there really is a worm in it
- the case where nobody is deceived by me because they know that I always tell lies
Lying and statements
Some philosophers believe that lying requires a statement of some sort; they say that the liar must actually speak or write or gesture.
Sisella Bok, author of a major philosophical book on the subject of lying, defines a lie as:
Others stretch the definition to include doing nothing in response to a question, knowing that this will deceive the questioner.
Others include 'living a lie'; those cases where someone behaves in a way that misleads the rest of us as to their true nature.
Why is lying wrong?
There are many reasons why people think lying is wrong; which ones resonate best with you will depend on the way you think about ethics.
- Lying is bad because a generally truthful world is a good thing: lying diminishes trust between human beings:
- if people generally didn't tell the truth, life would become very difficult, as nobody could be trusted and nothing you heard or read could be trusted - you would have to find everything out for yourself
- an untrusting world is also bad for liars - lying isn't much use if everyone is doing it
- Lying is bad because it treats those who are lied to as a means to achieve the liar's purpose, rather than as a valuable end in themselves
- Many people think that it is wrong to treat people as means not ends
- Lying is bad because it makes it difficult for the person being lied to make a free and informed decision about the matter concerned
- Lies lead people to base their decisions on false information
- Lying is bad because it cannot sensibly be made into a universal principle
- Many people think that something should only be accepted as an ethical rule if it can be applied in every case
- Lying is bad because it's a basic moral wrong
- Some things are fundamentally bad - lying is one of them
- Lying is bad because it's something that Good People don't do
- Good behaviour displays the virtues found in Good People
- Lying is bad because it corrupts the liar
- Telling lies may become a habit and if a person regularly indulges in one form of wrong-doing they may well become more comfortable with wrong-doing in general
- Some religious people argue Lying is bad because it misuses the God-given gift of human communication
- God gave humanity speech so that they could accurately share their thoughts - lying does the opposite
- Some philosophers say lying is bad because language is essential to human societies and carries the obligation to use it truthfully
- When people use language they effectively 'make a contract' to use it in a particular way - one of the clauses of this contract is not to use language deceitfully
What harm do lies do?
Lies obviously hurt the person who is lied to (most of the time), but they can also hurt the liar, and society in general.
The person who is lied to suffers if they don't find out because:
- They are deprived of some control over their future because
- They can no longer make an informed choice about the issue concerned
- They are not fully informed about their possible courses of action
- They may make a decision that they would not otherwise have made
- They may suffer damage as a result of the lie
The person who is lied to suffers if they do find out because:
- They feel badly treated - deceived and manipulated, and regarded as a person who doesn't deserve the truth
- They see the damage they have suffered
- They doubt their own ability to assess truth and make decisions
- They become untrusting and uncertain and this too damages their ability to make free and informed choices
- They may seek revenge
The liar is hurt because:
- He has to remember the lies he's told
- He must act in conformity with the lies
- He may have to tell more lies to avoid being found out
- He has to be wary of those he's lied to
- His long-term credibility is at risk
- He will probably suffer harm if he's found out
- If he's found out, people are more likely to lie to him
- If he's found out he's less likely to be believed in future
- His own view of his integrity is damaged
- He may find it easier to lie again or to do other wrongs
Those who tell 'good lies' don't generally suffer these consequences - although they may do so on some occasions.
Society is hurt because:
- The general level of truthfulness falls - other people may be encouraged to lie
- Lying may become a generally accepted practice in some quarters
- It becomes harder for people to trust each other or the institutions of society
- Social cohesion is weakened
- Eventually no-one is able to believe anyone else and society collapses
When is it OK to lie?
The philosopher Sissela Bok put forward a process for testing whether a lie could be justified. She calls it the test of publicity:
If we were to apply this test as a thought experiment we would bring together a panel of everyone affected by a particular lie - the liar, those lied to and everyone who might be affected by the lie.
We would then put forward all our arguments for telling a particular lie and then ask that 'jury' of relevant and reasonable persons if telling this lie was justified.
But what could we do in the real world?
- First inspect our own conscience and ask whether the lie is justified
- Second, ask friends or colleagues, or people with special ethical knowledge what they think about the particular case
- Thirdly, consult some independent persons about it
This sort of test is most useful when considering what we might call 'public' lying - when an institution is considering just how much truth to tell about a project - perhaps a medical experiment, or a proposed war, or an environmental development.
One executive observed to this writer that a useful test for the justifiability of an action that he was uncertain about was to imagine what the press would write afterwards if they discovered what he had done and compared it to what he had said in advance.
In most cases of personal small scale lying there is no opportunity to do anything more than consult our own conscience - but we should remember that our conscience is usually rather biased in our favour.
A good way of helping our conscience is to ask how we would feel if we were on the receiving end of the lie. It's certainly not foolproof, but it may be helpful.
Bok sets out some factors that should be considered when contemplating a lie:
- Are there some truthful alternatives to using a lie to deal with the particular problem?
- What moral justifications are there for telling this lie - and what counter-arguments can be raised against those justifications?
- What would a public jury of reasonable persons say about this lie?
Lying and ethical theory
Lying and ethical theory
Different theories of ethics approach lying in different ways. In grossly over-simplified terms, those who follow consequentialist theories are concerned with the consequences of lying and if telling a lie would lead to a better result than telling the truth, they will argue that it is good to tell the lie. They would ask:
‘Would telling the truth or telling a lie bring about the better consequences?’
In contrast, a dutybased ethicist would argue that, even if lying has the better consequences, it is still morally wrong to lie.
Consequentialists (Utilitarians) and lies
Consequentialists assess the rightness or wrongness of doing something by looking at the consequences caused by that act. So if telling a particular lie produces a better result than not telling it, then telling it would be a good thing to do. And if telling a particular lie produces a worse result than not telling it, telling it would be a bad thing to do.
This has a certain commonsense appeal, but it's also quite impractical since it requires a person to work out in advance the likely good and bad consequences of the lie they are about to tell and balance the good against the bad. This is hard to do, because:
- consequences are hard to predict
- measuring good and bad is hard
- how do we decide what is good and what is bad?
- for whom is it good or bad?
- what system of measurement can we use?
- what consequences are relevant?
- how long a time-period should be used in assessing the consequences?
- it requires a person to value everyone involved equally and not to give extra value to their own wishes
- it requires a person to consider the consequences to society in general of telling lies as well as the consequences for those actually involved
So most Utilitarian thinkers don't apply it on a case by case basis but use the theory to come up with some general principles -- perhaps along the lines of:
- Lying is bad, because
- it causes harm to people
- it reduces society's general respect for truth;
- but there are some cases - white lies or mercy lies - where it may be OK to tell lies.
This is an example of 'rule-utilitarianism'; considering every single action separately is 'act-Utilitarianism'.
These two forms of Utilitarianism could lead to different results: An act-Utilitarian might say that telling a lie in a particular case did lead to the best results for everyone involved and for society as a whole, while a rule-Utilitarian might argue that since lying made society a less happy place, it was wrong to tell lies, even in this particular case.
Deontologists base their moral thinking on general universal laws, and not on the results of particular acts. (The word comes from from the Greek word deon, meaning duty.)
An act is therefore either a right or a wrong act, regardless of whether it produces good or bad consequences.
Deontologists don't always agree on how we arrive at 'moral laws', or on what such laws are, but one generally accepted moral law is 'do not tell lies'.
And if that is the law then lying is always wrong - even if telling the truth would produce far better consequences: so if I lie to a terrorist death squad about the whereabouts of the people that they’re hunting, and so save their lives, I have in fact done wrong, because I broke the rule that says lying is wrong.
Most of us would accept that an unbreakable rule against lying would be unworkable, but a more sophisticated rule (perhaps one with a list of exceptions) might be something we could live with.
Virtue ethics looks at what good (virtuous) people do. If honesty is a virtue in the particular system involved, then lying is a bad thing.
The difficulty with this approach comes when a virtuous person tells a lie as a result of another virtue (compassion perhaps). The solution might be to consider what an ideal person would have done in the particular circumstances.
Philosophers on lying
Philosophers on lyingImmanuel Kant, 18th century portrait ©
Some philosophers, most famously the German Immanuel Kant (1724-1804), believed that that lying was always wrong.
He based this on his general principle that we should treat each human being as an end in itself, and never as a mere means.
Lying to someone is not treating them as an end in themselves, but merely as a means for the liar to get what they want.
Kant also taught 'Act so that the maxim of thy will can always at the same time hold good as a principle of universal legislation.' This roughly means that something is only good if it could become a universal law.
If there was a universal law that it was generally OK to tell lies then life would rapidly become very difficult as everyone would feel free to lie or tell the truth as they chose, it would be impossible to take any statement seriously without corroboration, and society would collapse.
Christian theologian St. Augustine (354-430) taught that lying was always wrong, but accepted that this would be very difficult to live up to and that in real life people needed a get-out clause.
St Augustine said that:
- God gave human beings speech so that they could make their thoughts known to each other; therefore using speech to deceive people is a sin, because it's using speech to do the opposite of what God intended
- The true sin of lying is contained in the desire to deceive
Augustine believed that some lies could be pardoned, and that there were in fact occasions when lying would be the right thing to do.
He grouped lies into 8 classes, depending on how difficult it was to pardon them. Here's his list, with the least forgivable lies at the top:
- Lies told in teaching religion
- Lies which hurt someone and help nobody
- Lies which hurt someone but benefit someone else
- Lies told for the pleasure of deceiving someone
- Lies told to please others in conversation
- Lies which hurt nobody and benefit someone
- Lies which hurt nobody and benefit someone by keeping open the possibility of their repentance
- Lies which hurt nobody and protect a person from physical 'defilement'
Thomas Aquinas also thought that all lies were wrong, but that there was a hierarchy of lies and those at the bottom could be forgiven. His list was:
- Malicious lies: lies told to do harm
- Malicious lies are mortal sins
- 'Jocose lies': lies told in fun
- 'Officious' or helpful lies
Lying under serious threat
Lying under serious threatIn a prison camp, lying can be used to gain an advantage ©
The reason for lying that gets most sympathy from people is lying because something terrible will happen if you don't lie. Examples include lying to protect a murderer's intended victim and lying to save oneself from death or serious injury.
These lies are thought less bad than other lies because they prevent a greater harm occurring; they are basically like other actions of justified self-defence or defence of an innocent victim.
The reasons why we think lies in such situations are acceptable are:
- The good consequences of the lie are much greater than the bad consequences
- Such lies are told to protect innocent persons who would otherwise suffer injustice
- Such lies are told to prevent irreversible harm being done
- Such situations are very rare, so lying in them doesn't damage the general presumption that it's wrong to lie
Since such lies are often told in emergencies, another justification is that the person telling the lie often has not time to think of any alternative course of action.
Threatening situations don't just occur as emergencies; there can be long-term threat situations where lying will give a person a greater chance of survival. In the Gulag or in concentration camps prisoners can gain an advantage by lying about their abilities, the misbehaviour of fellow-prisoners, whether they've been fed, and so on. In a famine lying about whether you have any food hidden away may be vital for the survival of your family.
Lying to enemies
When two countries are at war, the obligation to tell the truth is thought to be heavily reduced and deliberate deception is generally accepted as part of the way each side will try to send its opponent in the wrong direction, or fool the enemy into not taking particular actions.
In the same way each side accepts that there will be spies and that spies will lie under interrogation (this acceptance of spying doesn't benefit the individual spies much, as they are usually shot at the end of the day).
There are two main moral arguments for lying to enemies:
- Enemies do not deserve the same treatment as friends or neutrals, because enemies intend to do us harm and can't grumble if we harm them in return by lying to them
- Lying to enemies will prevent harm to many people, so the good consequences outweigh the bad ones.
Other types of lying
Other types of lying
This legalistic device divides a statement into two parts: the first part is misleading, the two parts together are true - however only the first part is said aloud, the second part is a 'mental reservation'.
Here are some examples:
- "I have never cheated on my wife" (except last Thursday)
- "I did not steal the cakes" (on Thursday afternoon)
- "I did not touch the painting" (but my glove did)
This device seems outrageous to the modern mind, but a few centuries ago it was much used.
One common occasion for mental reservations was in court, when a person had sworn an oath to tell the truth and expected God to punish them if they lied.
If they'd stolen some sheep on Tuesday they could safely tell the court "I did not steal those sheep" as long as they added in their mind "on Monday". Since God was believed to know every thought, God would hear the mental reservation as well as the public statement and therefore would not have been lied to.
Sissela Bok says that this device is recommended to doctors by one textbook. If a feverish patient, for example, asks what his temperature is, the doctor is advised to answer "your temperature is normal today" while making the mental reservation that it is normal for a person in the patient's precise physical condition.
Lying to those with no right to the truth
The Dutch philosopher and lawyer Hugo Grotius (1583-1645) taught that a lie is not really wrong if the person being lied to has no right to the truth.
This stemmed from his idea that what made a wrong or unjust action wrong was that it violated someone else's rights. If someone has no right to the truth, their rights aren't violated if they're told a lie.
This argument would seem to teach that it's not an unethical lie to tell a mugger that you have no money (although it is a very unwise thing to do), and it is not an unethical lie to tell a death squad that you don't know where their potential victim is hiding.
In practice, most people would regard this as a very legalistic and 'small print' sort of argument and not think it much of a justification for telling lies, except in certain extreme cases that can probably be justified on other grounds.
Lying to liars
If someone lies to you, are you entitled to lie to them in return? Has the liar lost the right to be told the truth? Human behaviour suggests that we do feel less obliged to be truthful to liars than to people who deal with us honestly.
Most moral philosophers would say that you are not justified in lying to another person because they have lied to you.
From an ethical point of view, the first thing is that a lie is still a lie - even if told to a liar.
Secondly, while the liar may be regarded as having lost the right to be told the truth, society as a whole still retains some sort of right that its members should use language truthfully.
But is it a pardonable lie? The old maxim 'two wrongs don't make a right' suggests that it isn't, and it's clear that even if the liar has lost their right to be told the truth, all the other reasons why lying is bad are still valid.
But there is a real change in the ethics of the situation; this is not that a lie to a liar is forgivable, but that the liar himself is not in a morally strong position to complain about being lied to.
But - and it's a big 'but' - even this probably only applies in a particular context - if I tell you lies about the number of children I have, that doesn't entitle you to lie to me about the time of the next train to London, although it would make it very hard for me to complain if you were to lie to me about the number of children in your family.
Nor does it justify lying to someone because you know they are an habitual liar - once again all the other arguments against lying are still valid.
Mutual agreed deception
There are cases where two people (or groups of people) willingly engage in a mutual deception, because they think it will benefit them. Sisela Bok puts it like this:
An example of this is a negotiation in which both parties will lie to each other ('that's my best price', 'I'll have to leave it then') in a way that everyone involved understands.
Lies that don't deceive are not sinful lies...or are they?
If both parties know that the liar's statement is NOT intended to be taken as a definitive and important statement of the truth then it may not count as a sinful lie, because there's no intention to deceive.
There are many cases where no reasonable person expects what is said to them to be genuinely truthful.
That may let us off the hook for things like:
- Flattery: 'you look lovely'
- Gratitude: 'that's just what I wanted'
- Formal language conventions: 'sincerely yours', 'pleased to meet you'
- Bargaining: 'my best price is £500'
- Generalisation: 'it always rains in Manchester'
- Advertising: '#### washes whitest'
- If believing the advert might lead to bad consequences - for example in medical advertising - this would not count as a guilt-free lie.
- Jokes: 'there was an Englishman, an Irishman and a Scotsman'
- Unpredictable situations: 'it won't rain today'
- Sporting tips: 'Pegleg is unbeatable in the 3:30 race'
- False excuses: 'he's in a meeting'
- Conjuring tricks: 'There's nothing up my sleeve'
It's not always easy to see the difference between these statements and white lies.
Incidentally the Ethics web team disagreed amongst themselves as to the status of lies that don't deceive - your thoughts are very welcome.
A white lie is a lie that is not intended to harm the person being lied to - indeed it's often intended to benefit them by making them feel good, or preventing their feelings being hurt.
For example, I go to a dinner party and my hostess asks how I like the dish she's prepared. The true answer happens to be 'I think it tastes horrible' but if I say 'it's delicious' that's a white lie. Most people would approve of that white lie and would regard telling the truth as a bad thing to do. (But this lie does do some harm - the hostess may feel encouraged to make that dish again, and so future guests will have to suffer from it.)
White lies usually include most of these features:
- they are not intended to harm the person lied to
- they are not intended to harm anyone else
- they don't actually harm anyone (or only do trivial harm)
- the lie is about something morally trivial
- they aren't told so often that they devalue what you say
White lies are not a totally good thing:
- the person being lied to is deprived of information that they might find useful even if they found it unpleasant
- the person telling the lies may find it easier to lie in future and they may come to blur the boundary between white lies and more blameworthy lies
White lies weaken the general presumption that lying is wrong and may make it easier for a person to tell lies that are intended to harm someone, or may make it easier to avoid telling truths that need to be told - for example, when giving a performance evaluation it is more comfortable not to tell someone that their work is sub-standard.
Lying and medical ethicsPatients must have the facts and understanding they need to make an informed choice ©
Lying and medical ethics
Health professionals have to reconcile the general presumption against telling lies with these other principles of medical ethics. While healthcare professionals are as concerned to tell the truth as any other group of people, there are cases where the principles of medical ethics can conflict with the presumption against lying.
The fundamental principles of medical ethics are:
- Respect for autonomy: acknowledging that patients can make decisions and giving them the information they need to make sensible and informed choices
- Doing no harm: doing the minimum harm possible to the patient
- Beneficence: balancing the risks, costs and benefits of medical action so as to produce the best result for the patient
- Justice: using limited medical resources fairly, legally and in accordance with human rights principles
Telling the truth is not an explicitly stated principle of most systems of medical ethics, but it is clearly implied by the principle of respect for autonomy - if a patient is lied to, they can't make a reasoned and informed choice, because they don't have the information they need to do so.
Respect for patient autonomy is particularly important in the case of people who are terminally ill, as they are likely to be particularly vulnerable to manipulation of the truth.
So why might healthcare professionals want to lie 'for the good of patients', and what are the arguments against this sort of lying?
- Lying may be good therapy: the doctor may believe that the patient should only be given information that will help their treatment
- Lying deprives the patient of the chance to decide whether they want the treatment - highly intrusive treatment near the end of life may prolong life, but at greatly reduced quality, and the patient, if properly informed, might decline such treatment
- The truth may harm the patient: a patient may, for example, give up hope, go into a decline or suffer a heart attack if given a depressing diagnosis and prognosis - they may even choose to kill themselves
- Such information should be given in a way that minimizes harm -- the patient should be appropriately prepared to receive the information and given proper support after being given bad news
- Surveys suggest that patients don't in general go into a severe decline or choose to kill themselves
- Respect for autonomy requires the patient to be given the chance to consider all legal courses of action, no matter how undesirable other people may think they are
- Lying deprives the patient of the opportunity to take meaningful decisions about their life, based on accurate medical information
- The patient may realise that the symptoms they experience and the way their disease progresses don't fit what they have been told. They then experience all the bad consequences of being lied to
- The patient wants to be lied to
- Surveys suggest that the majority of patients want to be told the truth, even if it's bad
- The patient won't properly understand the truth
- It's the duty of the professional to communicate the truth in a way that each particular patient can understand, and to check that they really have understood it. (Honesty and intelligibility are particularly important when obtaining patient consent for a particular treatment or procedure.)
- The patient would go into denial and resist the truth if they were told it
- Many patients don't go into denial
- The patient still has the choice to go into denial
- Denial may be an important stage of coming to terms with the inevitable; the patient should not be deprived of the chance of working through it and dealing with their life-situation
- There is no certain truth: the future course of a disease is almost always uncertain
- The professional should give the patient the range and likelihood of possible outcomes
- The doctor doesn't want to bring the patient bad news
- This seems more for the benefit of the doctor than the patient
- Telling the patient the truth may cause the patient to use up more of the healthcare professional's time than telling a lie, when this time could more beneficially be spent on other patients
- Putting proper patient support systems in place will deal with this
Obtaining informed consent
Healthcare professionals must tell the truth and make sure that the patient understands it properly when they are obtaining the patient's consent to a procedure or treatment.
If the patient is not told the truth they cannot give 'informed consent' to the proposed course of action.
A patient can only give informed consent if they know such things as the truth about their illness, what form the treatment will take, how it will benefit them, the probabilities of the possible outcomes, what they will experience during and after the treatment, the risks and side-effects, and the qualifications and track-record of those involved in the treatment.
There is also evidence that patients do better after treatment if they have a full understanding of both the treatment and the illness, and have been allowed to take some participation and control of the course of their treatment.