Aristotle's On Interpretation Ch. 9. segment 18a34-19a7: If an assertion about a future occurence is already true when we utter it, then the future has been predetermined and nothing happens by chance

(18a34-19a7) of Ch. 9 If an assertion about a future occurence is already true when we utter it, then the future has been predetermined and nothing happens by chance

In Ch. 4 Aristotle instructs us that an assertion may either be true or false. We call an assertion “true” when what it signifies, i.e. its meaning (νόημα), corresponds to the circumstances which underlie it. Conversely, we call an assertion “false” when its meaning does not correspond to the circumstances which underlie it. By way of illustration, insofar as the assertion “Nicomachus is brave” is true, it is necessary that he be brave. It cannot be any other way. In fact, if Nicomachus is not brave, then to assert that he is brave is not true but false. In this way, if it is true to assert that “Nicomachus is brave”, there is no chance that he is not brave. He is brave by necessity.

(i) On the assumption that an assertion about the future is already true or false when we utter it

Now, if every assertion is either true or false, then what each and every assertion signifies either happens or does not happen to be the case. From this we may make the case that once we assert something about the future, what we assert will already either be true or false. Yet, if an assertion about the future is true or false when we utter it, then every future event has been predetermined and nothing happens by chance. For example, suppose that before Nicomachus was born, his father proclaimed “my son will fight against the Persians.” If Nicomachus is fighting against the Persians now, then, according to this logic, it follows that what his father asserted twenty years ago is not only true now but was already true before Nicomachus was even born. Yet, if it was true then, it was necessary (a) for Nicomachus’ father to have a son, (b) for his son to grow old enough to become a soldier, (c) for Persian troops to engage in a fight with those Greek troops in which Nicomachus serves at this moment. In other words, if what the father of Nicomachus asserted was already true twenty years ago, then (a), (b) and (c) were bound to happen and it was impossible for any other occurence to come about in their stead.

(ii) On the assumption that assertions about the future are never true 

At this point, we may come to argue that no assertion about the future is true. This claim leaves us worse off than the previous one, however. For the sake of argument, if every assertion about the future is false, then everything must occur in such a way that no assertion ever proves true. Afterall, if the assertion “Nicomachus will fight tomorrow” is false today, then it has already been determined that Nicomachus will not fight. Yet, if every assertion is false, then the contradictory “Nicomachus will not fight tomorrow” cannot be true either. This leads to a paradoxical situation where it is necessary for Nicomachus to both ‘not fight’ and ‘not not fight’ tomorrow so that both assertions remain false. All things considered, Nicomachus will have to either fight or not fight tomorrow. At some point, either “Nicomachus will fight tomorrow” or “Nicomachus will not fight tomorrow” will inevitably prove true.

We thereby arrive at the conclusion that both (i) the assumption that assertions about a future occurrence are already true or false when uttered, and (ii) the assumption that such assertions are always false, lead us to absurdity. To begin with, we have established that if every assertion is already true or false when we utter it, then the future has already been set. Yet, If every future event unfolds according to a predetermined plan, then we have no reason to exert ourselves in thinking ahead or making plans for tomorrow. As such, what we need to understand is that it is not the truth or falsity of any assertion which sets how the future unfolds. As a matter of fact, it is the other way around. It is what happens which determines which assertions are true and which are false. What an assertion about a future occurrence signifies cannot already be true or false when we utter it. This is because the set of circumstances which corresponds to it has not yet come about. As such, an assertion about the future is no more than a prediction about what will be or will not be.

We shall pursue to gain a more thorough understanding of this as we push onward with Ch. 9.

Key points: (i) An assertion may be true or false. (ii) An assertion is true when its meaning corresponds to the set of circumstances underlying the assertion and false when it does not.  (iii) If assertions about future occurrences are already true or false when we utter them, then the future has been predetermined and nothing happens by chance. (iv) Be that as it may,it is not the truth or falsity of an assertion which determines what will happen or what will not happen. Instead, it is through what happens that we can decide which assertion is true and which false. (v) As such, assertions about future events cannot be already true or false when we utter them. This is because the set of circumstances which corresponds to them has not yet come about. They are no more than predictions about what will be or will not be.

“Columns of the Parthenon” by Frederic Edwin Church ca. 1869