Aquinas, Thomas

In “Question 110: Secunda Secundae Partis” of his magnum opus, the Summa Theologica, medieval philosopher and theologian St. Thomas Aquinas (c.1225–74) discusses lying with the kind of definitional precision and logical rigor that one expects from a Scholastic scholar. Aquinas argues that all lies by definition oppose the truth. He claims that they do so materially because what is conveyed is false in some essential way: formally, in that it is the desire of a liar's will to convey this falsehood to another; and effectively, to the extent that the liar is successful in causing another to believe true what the liar thinks is false.

Aquinas acknowledges that lies need not be verbal. The manipulation of signs with the intention to deceive constitutes lying, even in the [Page 32]absence of words. Planting forensic evidence to incriminate an innocent person or hiding evidence of guilt are examples of such nonverbal manipulation. In Aquinas's view, the intention of the liar to deceive is an important component of the sin of lying. For this reason, a liar's conveying an objective truth in such a way as to create a false impression, and thus deceive another, is still defined as a lie by Aquinas. As he explains, while such communication might materially and accidentally be connected to the truth, in its intent and its effect, it remains formally and essentially a falsehood, and is therefore a lie.

As a contemporary example of this view, a student tells her mother that she stayed at The Library (a bar near campus) until 2:00 a.m. While factually true, the absence of any mention that The Library is a bar leaves the mother with a false impression of the way that her daughter spent the evening. Conversely, if a person conveys something that is objectively false, wrongly thinking it true, then he or she is not guilty of lying. Such is the case, for example, when a person reports that the solar system has nine planets, unaware that the count is now eight because scientists demoted Pluto to dwarf planet status in 2006.

According to Aquinas, all lies fall into one of three categories: officious, jocose, and mischievous. Officious lies are instrumental means of accomplishing some goal; jocose lies are told with the intent of entertaining; and mischievous lies, have as their object harm directed toward another. As a moral theologian, Aquinas is adamant that lying is always sinful. However, he is pragmatic enough to recognize that there are circumstances when it might be deemed necessary to lie in order to promote some positive good or avoid a greater evil. While Aquinas holds that lies told for such reasons are still sinful, he admits that the demands of difficult circumstances mitigate, though they do not totally negate, the sinfulness of the act.

He uses biblical examples to illustrate this point: Abraham referring to his wife Sarah as his sister while in Egypt, Jacob deceiving his father into giving him his older brother's birthright, the midwives of Egypt lying to the Pharaoh in order to save Jewish males, and Judith deceptively gaining the trust of Holofernes so that she can slay him and save her people. Like all lies, these are sinful violations of God's law, despite the positive consequences that resulted from them. They are wrong, as Aquinas explains, in much the same way that it is wrong to steal, even if one's intention is to give the ill-gotten money and goods to charity.

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