Prejudices (Latin praejudicia, French préjugés; usually translated as “preconceived opinions” in CSM) are opinions that we accept not because we have clearly perceived that they are true but as a result of earlier judgments we have made (AT IXA 204, CSM II 270). The Latin term preajudicia literally means “prejudgments.” Descartes explains that the proposition “whatever thinks, exists” can be described as a prejudice when we put it forward without attention and believe it to be true only because we remember having previously judged it to be so. If we examine the proposition and believe it to be true because it is evident to the understanding, then it is not a prejudice (AT IXA 205, CSM II 271). So a prejudice is an opinion that is accepted without sufficient reason, but not everything accepted without sufficient reason is a prejudice. The first time I assent to something I do not clearly understand, the opinion I form is not a prejudice, but it becomes one if I continue to affirm it simply because I did so in the past.

We are able to form the kind of judgments that give rise to prejudices because we can choose to affirm what we do not clearly perceive (AT VIIIA 18, CSM I 204–5). The natural light of reason tells us that we should not do this (AT VIIIA 21, CSM I 207; cf. AT VII 60, CSM II 41), but Descartes identifies several ways in which it can occur. In childhood, we do not have full use of our reason and cannot examine the basis for our judgments (AT VIIIA 5, CSM I 193). In adulthood, we may forget that we should not judge where we do not clearly perceive (AT VII 62, CSM II 43). Through carelessness and inattention, we may not notice the obscurity or confusion in our perception (AT VIIIA 21, CSM I 206). Through rashness and an eagerness to find the truth, we may assent to something that we do not fully comprehend (AT VIIIA 21, CSM I 206–7).

These ill-considered judgments give rise to prejudices if we continue to affirm them. Presumably inattention, rashness, and lack of reason can play a role here too. And we may be unwilling to change our minds through laziness or stubbornness (AT VII 377, CSM II 259).