 If Descartes does hold that there are things that could be but are not, his view still demands the important qualification discussed in the first section above. He of course realizes that in everyday discourse we speak of things that can happen but don’t. However, if our understanding of these things is not clear and distinct, and if our understanding of them as possible is not clear and distinct, then Descartes will not introduce them as possibilities. Descartes appreciates that according to common ways of speaking, all kinds of things are possible. As we have seen, he considers this concept of ‘possible’ after Mersenne introduces it in Second Objections: