Generally, any fallacy or error in reasoning. In Kant, the four paralogisms of pure reason attempt to show

1. (i) that the soul is a substance;

2. (ii) that it is not an aggregate, but simple;

3. (iii) that it is one and the same subject at different times; and

4. (iv) that it is conscious of the existence of itself only, and of other things only as representations.

These are examples of reasoning beyond the bounds of possible experience, and result (especially in Descartes and the rationalists) from misinterpreting what is given by ‘I think’. That Descartes misunderstood this had been charged before, notably by Gassendi and Lichtenberg, but Kant is credited with the definitive treatment.