Can Irrational people Be Persuaded with Rationality?

[Angrboda]

Well, first I'd have to know what you mean by rational and irrational. I personally am of the opinion that both concepts are incoherent and don't correspond to any actual thing. But that caveat aside, people's rationality has multiple dimensions. First, a person may be more or less rational towards a broad spectrum of questions due to the transitory or semi-permanent duration of things like strong emotion, episodes of mental illness, the influence of hormonal states and so on. Also, a person may be more or less capable of thinking rationally about all subjects regardless of content if they are unintelligent, uneducated, have intellectual stengths which they preferentially apply to reason and so on. (I'm an example of the latter. I'm relatively poor at formal reasoning, so I lean on feeling and intuition as my primary guide.) Furthermore, people can be rational about one thing, yet irrational about another; reason is somewhat domain dependent. For example, I have a chronic mental illness which results in, according to others, delusional beliefs; if you were to challenge the substance of those delusions, you'd find I can be quite irrational in their defense despite being rational about other, unrelated propositions.

To bring this to bear on your original question, it may be ineffective to challenge a person regarding beliefs or claims that they are incapable of thinking rationally about, however since in most people such regions are localized in their thinking, even if they are irrational in that region, you may challenge them rationally about which they are capable of reasoning rationally, and, for which, the rational region provides important support for continued maintenance of the irrational region or belief. (See the Duhem-Quine thesis, aka Underdetermination of Theory, aka epistemological holism.) Note that this is how deconversion from religious belief typically occurs, by persuading someone on an issue at the periphery of their irrational belief, and successfully replacing the irrational account with a rational one; repeating this process over time eventually leads to there no longer being any periphery, and not enough center to keep the irrational belief in place.