The Greek philosopher Plato (427/8-347/8 BCE) claimed that there was an objective, undeniable truth which one needed to recognize in order to live a full life. In his famous work Republic, Plato discusses the importance of justice but, as always, defines `true justice' according to his standard of objective truth. One of the largest obstacles in recognizing either truth or justice, or any good at all, is the lie in the soul which Plato defines in Republic Book II.
Simply put, to have `the lie in the soul' means to believe wrongly about the most important things in one's life. To rid oneself of this lie one must, first, acknowledge that it is there and then work towards removing it and replacing with truth and a proper understanding. My article, published through Ancient History Encyclopedia, clarifies this concept further.
The link to the article is here: http://www.ancient.eu.com/article/210/
And the article begins:
In his famous work Republic, Plato discusses the concept of the `True Lie' or the `Lie in the Soul'. Through a conversation between Socrates and Adeimantus (Plato's brother) Plato defines the `true lie' as believing wrongly about the most important things in one's life. The `lie in the soul' can be understood as Plato's answer to the Sophist Protagoras' famous assertion that "Man is the measure of all things", that, if one believes something to be so, it is so. Plato repudiated Protagoras' claim in virtually every one of his dialogues and Republic is no exception.
The `true lie' or `lie in the soul' can best be explained this way: If one believes, at a certain point, that eating carrots with every meal is the best thing one could do for one's health and, later, realizes that excess in anything can be a bad thing and stops the carrot-eating, that realization would have no long-term negative consequences on one's life. If, however, one believes the person one loves is a paragon of virtue and then discovers that person is a lying, conniving thief, this discovery could undermine one's confidence in oneself, in one's judgment, in other people, and even in a belief in God, in so far as finding out one is wrong about a person one was so certain of would lead one to question what other important matters in life one is also wrong about...