"Chapter 9". Of contradictory propositions about the past and present, one must be true, the other false. But when the subject is individual, and the proposition is future, this is not the case. For if so, nothing takes place by chance. For either the future proposition such as, 'A sea battle will take place,' corresponds with future reality, or its negation does, in which case the sea battle will take place with necessity, or not take place with necessity. But in reality, such an event might just as easily not happen as happen; the meaning of the word 'by chance' with regard to future events is that reality is so constituted that it may issue in either of two opposite possibilities. This is known as the problem of future contingents.