Deceit is “an act of keeping the truth hidden, especially to get an advantage” (Cambridge Dictionary). This means that people deceive with a purpose. They want something and think that only by deceiving others will they get what they want. “Hidden the truth” can mean “lying” or “omit”, although some people say that “omitting” is a way of “lying”. There are many reasons for lying or omitting. In fact, deceiving is a daily activity. From little lies (for example, telling someone we meet on the street that we are fine when we are not), to living a double life and lying about it to everyone. Some say that a lie is a lie and it doesn’t matter if it is a little one or a big one. Some say that those who tell little lies are also capable of telling big ones. The truth is: everyone lies.

Treachery is the worst kind of deceit. According to the Cambridge Dictionary, it is the “behaviour in which a person deceives someone who trusts them”. The main difference from a “simple lie” is related to “trust”, that is, you are lying to someone who believes in you, who thinks you are being true and cares about you. For example, if you say you are fine to someone you find on the street, this person doesn’t necessarily trust you or really cares. Treachery is like stabbing someone’s trust. The deceit is more serious and, thus, has more dramatic consequences once revealed. This is valid regarding personal relationships and actions against one’s own country. In the latter, it is called treason and it is considered a crime. Spies deliberately pretend to be someone they are not in order to gain the trust of those who possess the information they need to pass on to the enemies. The enemies, thus, get an advantage they wouldn’t otherwise.

People can betray the trust of other people in other contexts, like in friendship or in love. They can also betray their own principles and values, when they act against what they believe and/or against their own feelings. Sometimes, people even lie to themselves. This means that one can betray themselves knowingly or they can find arguments to justify it (hence, lying). Honesty with oneself and with others is very difficult due to various reasons such as expectations, pressure, fear, politeness, shame, wanting to be accepted or to belong… even feelings of wanting to protect oneself or others.

Another type of deceit is manipulation, which is “to control someone or something in a clever way so that they do what you want them to do” (Cambridge Dictionary). This can be done by distorting the truth so the other person believes in false information and acts accordingly. In this case, it’s not just about deception, but also control. People can manipulate other people, but a State or an Institution can also manipulate a large number of people. In the latter, you can say they are “brainwashing”.