Enlightenment is man's emergence from his self-imposed immaturity. Immaturity is the inability to use one’s understanding without guidance from another. This immaturity is self-imposed when its cause lies not in lack of understanding, but in lack of resolve and courage to use it without guidance from another. Sapere Aude! (Kant: An Answer to the Question: What is Enlightenment?)

Kant’s famous definition of the enlightenment may be read as a maxim of critical thinking: To have the courage to use your own understanding. But what does that even mean?

The philosophical term critique or criticism derived from the Old Greek word of κρίνειν for distinguishing or putting something asunder denotes a capacity to systematically question claims of truth. Critique denotes the human capacity to rationally form a judgement as the result of a process of cognition in a fair-minded way. Thinking is the opposite of mere parroting or accepting other peoples’ beliefs without diligently checking the issue first.

Critical thinking is contrary to any dogmatism and ideology and can thusly prove to be an effective protection against manipulation, obedience and fallacy. Everyone is able to think, but is the same true for critical thinking? Or to put it differently: What kind of critical thinking skills are needed?

...to use his own reason in all matters of conscience [...] and for each person’s calling to think for himself.

Critical thinking is independent and free without any boundaries, it is formally logical, rational (not emotional) and self-imposed without succumbing to moral bias, attribution or ideological influence through others. It is (reflective) thinking for oneself.

How can this kind of thinking be cultivated? Logic defined by Quine as „the logistic doctrine of logical truth”1 is a good starting point for practicing critical reasoning and exercising one’s thinking skills. There is a difference between an argument and a claim in classical logic. But what is an argument? An argument consists of a set of premises and one conclusion. The goal is to epistemically justify a statement. Epistemic reasons are reasons that provide logical justification for a statement. This doesn’t hold true for rhetoric where the argument (as λόγος) is just one of several technical means of persuasion and good reasons are made effective when used together with ἔθος and πάθος.

A good argument is one whose premises make the conclusion2 likely to be true (premises support the conclusion). A single claim, claims jumbled together without any logical relation and conclusion, a narrative or an explanation are not an argument. Furthermore, the difference between fact (verifiable if “true” or “false”) and value (“great” or “terrible”) plays a big role within critical thinking. At first glance, both are statements, however value judgements have either aesthetic, practical or moral implications. Why is this distinction important? It is common to mix moral judgements with aesthetic ones in rhetorical argumentation such as speeches with far reaching consequences: Whereas the aesthetic judgement is individual, subjective and as such cannot be erroneous (question of taste), the moral judgement (commands) holds for everybody, but can be erroneous. If one is being mixed with another, a moral validity is wrongly implied or a subjective judgement is attempted to be justified as being objectively valid. Why is it important in a court hearing if the female victim did wear a skirt or not? A skirt is a fashion item that can be discussed by aesthetic rather than moral standards, even if this is exactly what happened in the early 60s with the invention of the miniskirt. A skirt in itself cannot be right or wrong, it can be stylish or ugly depending on the eye of the beholder. This mix-up doesn’t make any sense under purely logical reasoning but in everyday life different types of values often go hand in hand for rhetorical reasons.

What does that mean for critical thinking?

Kant defined critical thinking as the „freedom to use reason publicly”3 without interference of anyone and as an inalienable right4. Thus, it may be seen as our human responsibility to courageously defy mainstream views when necessary. In this respect, crtitical thinking is the polar opposite of „assisted thinking”5 and as such not to be underestimated but to be fostered and institutionally allowed for.

1 Willard van Orman Quine: Philosophy of Logic. p. 7.

2 There are inductive and deductive arguments/conclusions.

3 Kant: Was ist Aufklärung? What is enlightenment? p.17.

4 Ibid, p. 14.

5 Michael Bröning: “Betreutes Denken: Weshalb die letzte Generation die offene Debatte verhindert”, in: Neue Züricher Zeitung, 08.02.2023, unter: https://www.nzz.ch/meinung/weshalb-die-letzte-generation-die-offene-debatte-verhindert-ld.1724874; last access: 02.09.2023.