If falsehood, like truth, had only one face, we would be in better shape. For we would take as certain the opposite of what the liar said. But the reverse of truth has a hundred thousand shapes and a limitless field.—Montaigne, Essays
What is deception
There are few definitions of deception. According to Merriam-Webster dictionary it is “an act or statement intended to make people believe something that is not true” . According to Ekman , the deception involves acting in such a way which leads another person to believe something, that you, yourself, do not believe to be true.
These definitions are broad. For example, if you think withholding information is not deception, you are mistaken. If you are acting in front of someone so, that you expect to present yourself in a certain way, you are deceiving that person. For example, if you like a girl of your friend, but you are not acting that way, you are deceiving your friend and the girl.
Ethics of deception
This bring up the question, Is deception acceptable? It certainly is. At least from the perspective of science, it is even necessary. According to Taylor & Shepperd , 81 percent of published psychological studies use deception. And it is only logical. If you are studying some psychological phenomenon, you could influence the result of it if you have told the participants about what are you trying to achieve. So deception becomes necessary.
Or in double blinded tests used mainly in medical research, deception is also necessary. But you cannot lie to subjects in medical experiments. It is against to law and also it is considered unethical . So if you cannot lie to a subject telling them you are giving them medicament if in reality you are not, how do you do double blinded test? You deceive the subject. You tell them that they have 50 percent chance that they are receiving the true medicament and 50 percent chance that they are receiving placebo. You have not lie to them, but you have deceived them, because you have not told them the whole truth.
But is deception acceptable in social interactions? Some forms of deceptions are against the law such as frauds or tax pay evasion, so clearly not all forms of deceptions are acceptable, just as in scientific research. But it is also obvious, that deception is useful and acceptable in some social interactions. If your sick partner asks you how do they look, you are probably going to lie to them or at leas deceive them and you would not tell them how they really look to you. Great usefulness of deception is shown in the movie The Invention of Lying, which is set in a society where everybody is telling the truth all the time. If you ever tried to imagine what would such world look like, you certainly have to watch the movie or at least this video.
Invention of Lying – Ricky Gervais from Rui Batista on Vimeo.
For example, almost all the movies except from documentaries are deception. The actors are pretending to be someone they are not and they know they are not them. So they use deception, which they could not if they were not able to deceive.
Subjectivity of deception
This brings interesting question regarding Ekman  definition, which suggest, that if you are deceiving somebody, you have to act or say something that you, yourself, do not believe to be true. So if you personally believe that you are Henry V., would you be able in a society in which no one can lie play Henry V. in a movie? You are not deceiving anyone, because you do believe that you are the Henry V. But nobody else in such society would be able to differentiate.
The reason we consider persons that believe they are someone that they are obviously not such as historical or fictional characters as mentally ill is result of the fact, that we are able to differentiate between the reality that is and the reality someone has made up.
If you are not able to differentiate between reality and deception, you are able to believe anything somebody tells you. So deceptions is clearly useful at least as protection from situations when someone else is trying to deceive us and to tell if somebody is deceiving us or simply has mental disorder.
You probably would not lock up in mental institution Johnny Depp for playing Jack Sparrow in a movie, but if he was going around the streets preaching that he in fact is Jack Sparrow for some time, you would quickly reconsider.
Types of deception
So we have already discussed usefulness of deception and differentiate what is deception and what is not. But as we mentioned, there is not just one form of deception.
There is a moment in the movie Insurgent where Tobias ask the leader of Candor faction, which is know for its truthfulness (I am paraphrasing)
– “I’ve heard you use truth serum in your initiation process”
– “We do not discus such matters with outsiders.”
– “That’s not an honest answer.”
– “Evasion of question is not the same as lying.”
And that is the truth. But lying is not the same as deception. Lying is a part of what deception means. It is the most know and recognizable part, but it is not all. Few examples could be 
- Lies: making up information or giving information that is the opposite or very different from the truth.
- Equivocations: making an indirect, ambiguous, or contradictory statement.
- Concealments: omitting information that is important or relevant to the given context, or engaging in behavior that helps hide relevant information.
- Exaggerations: overstatement or stretching the truth to a degree.
- Understatements: minimization or downplaying aspects of the truth.
but the categorization could be based on many different factors considering circumstances. For example considering on-line interactions “there are various types of possible deception such as category deception (gender switching), attractiveness deception, or identity concealment” .
Deception requires the person that is deceiving to have contradictory knowledge about his actions or statements, so someone who is telling obvious lies but believes them to be true is in fact not deceiving us. Also, lies are not the only form of deception and deception is any form of “not truth telling” including withholding information. Also deception is useful in scientific research and in some social interactions, but also unacceptable and punished in some cases. Knowledge of deception is also useful tool for its recognition.
So live happily and be truthful to yourself.
 Ekman, P. (1985). Telling lies. New York : W. W. Norton.
 Ortmann, Andreas, and Ralph Hertwig. “Is deception acceptable?.” (1997): 746.
 Taylor, Kevin M., and James A. Shepperd. “Probing suspicion among participants in deception research.” American Psychologist 51.8 (1996): 886.
 Wendler, Dave. “Deception in medical and behavioral research: is it ever acceptable?.” The Milbank Quarterly (1996): 87-114.
 Utz, Sonja. “Types of deception and underlying motivation what people think.” Social Science Computer Review 23.1 (2005): 49-56.