The problem of compatibility or incompatibility between the possibility of meaningful deliberation and necessitarianism (the view that everything happens of necessity) has long been a topic of discussion, and it is well known that Aristotle is concerned with the problem in De Interpretatione 9. He thinks that if everything happens of necessity (18b30-31), then ‘there would be no need to deliberate or to take trouble, thinking that if we do this, this will happen, but if we do not, it will not’ (18b31-33). In this paper, I argue that Aristotle is a deliberation incompatibilist, and consider why he thinks that it is reasonable to endorse this position.
First, I show that it is more reasonable to think that Aristotle here gives a reductio, and to supply some implicit premises to the necessitarian argument (18a34-18b16) from which he can validly conclude that everything happens of necessity, rather than interpreting it as a fallacious inference made by his opponent (pace Bobzien 2011; Nielsen 2011). In my view, Aristotle thinks that deliberation is inefficacious if the future is necessary (in the sense of being fixed or irrevocable) in the way the past and present are.
Second, I argue that the necessitarian conclusion that ‘everything is and happens of necessity’ (18b30-31), which is considered to be incompatible with deliberation, should be distinguished from the view that everything that happens happens of necessity, independently of antecedent conditions, as well as from the view that everything that happens is necessitated by antecedent conditions (pace Nielsen 2011). Further, I also show that Aristotle’s argument on the inefficaciousness of deliberation is not a sort of ‘Lazy Argument’ (pace Sorabji 1980).
Third, I argue that, in Aristotle’s view, the principle that ‘if we do this, this will happen, but if we do not, it will not’ (18b31-33) would hold even if everything happens of necessity. It is important to note that the necessitarian conclusion is compatible with this principle, and that Aristotle does not say that the principle would not hold if everything happens of necessity, even though he thinks that deliberation on the basis of the principle would not be needed in such a case (18b31-33). By pointing out that Aristotle accepts that one could still ‘causally affect some future events’ even if everything happens of necessity, I show that Fine’s (1984) contention that ‘since one can causally affect some future events, one can deliberate about them’ misses the point.