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Logic and the Stoics II

 




A philosopher named Diodorus Cronus may properly be considered the first Stoic. He usually isn't. That title is usually given to Zeno of Citium -- not to be confused with the Achilles-and-the-tortoise guy of Elea. Diodorus is a sort of middle link between the two famous Zenos. He might have known the Eleatic, he certainly in later life knew the fellow of Citium

The second Zeno was professedly a student of Diodorus, and some of Diodorus' teachings that come down to us seem distinctively Stoic already that it seems unnecessary to wait until Zeno's maturity to give them a distinctive name. So, let's just call Diodorus the first Stoic.

One of his contributions is what is known as the "Master Argument." This consists of three propositions, and  the key point is that the first two together disprove the third.

1) every true proposition about the past is necessary;

2) the impossible does not follow from the possible,

3) something is possible which neither is true nor will be true. 

Perhaps yesterday an admiral gave an order to his fleet to sail into dangerous waters, patrolled by the ships of a foe. The first proposition says that either this happened or it didn't. That is binary if the proposition itself is free of vagueness (we agree exactly on who counts as an admiral, etc.) So if it is that case that yesterday an admiral gave this order, then that is a necessary proposition. There is nothing contingent about it as of today! 

The second proposition is, as I understand it, a statement about cause and effect as well as of logic. Since everything that is or ever has been actual is possible, we can safely say that every state of affairs has been a possible that followed from a preceding possible, which followed from a preceding possible, and so forth. There has been no impossible state of affairs in this chain moving backward, and there will be none moving forward either.

Now for the third proposition. Suppose we think of a sea battle tomorrow. Perhaps it will arise because of the order that the Admiral gave to his fleet yesterday. Now, we may naively think that it is POSSIBLE the battle will happen, and it is also POSSIBLE that it will be avoided. This, too, is binary if the terms are well defined. One of these will happen. The battle will either take place, or it will be averted. If both of those are possible, then "something is possible which neither is true nor will be true." If there is a battle, we might want to say that it could possibly have been averted, although the peaceful day at sea expressed in that possibility will not (have been) true. 

In other words, on the day after tomorrow we will want to say (according to Diodorus) that the statement "there was a sea battle yesterday" is a necessary truth. If it is going to be a necessary truth then, it must be one now.

The Master Argument (the particulars of which are not known to us, although I've just offered a reasonable reconstruction) appears to have been an argument that if we want to preserve our belief in (3), we will have to abandon either (1) or (2), and it is better to keep both of them and abandon (3). 

Maybe I'm wrong. I could be getting this all wrong. You can read more about it and correct me if necessary, here:

Dialectical School (Stanford Encyclopedia of Philosophy)

All this has everything to do with the distinction modus tollens I discussed yesterday. A variation on the "spicy cooking" example I used yesterday might run this way:

If the sea battle were fated then it would have happened.

The sea battle did not happen.

Thus, the sea battle was not fated.  

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