New Essay
Volume 3
Appendix 2. (fn. 23)
[Sextus' refutation of scepticism]
Sceptics do not deny appearances. Hence they do not deny knowledge but say it lacks certainty. They attack the truth of knowledge at its base, the ultimate principle of certainty. We should consider carefully the following passage of Sextus where he claims to oppose the dogmatists:
If something (which the dogmatists say is the most general conception of all (ka m¢nt¿ t, Åper fasn eµnai p7ntwn genik3/4taton) is false, they must accept that all other things are false. For example, if we grant the general proposition, 'That which is animal has a soul', we must also grant the other proposition: 'This (particular) thing that is animal has a soul'; in the same way, if the most universal conception of all (something) is false, every particular conception will be false, and there will be no truth.
Scepticism is totally bent on demonstrating that something (the most universal notion and principle on which all other conceptions depend) cannot be shown to be true, and that consequently all knowledge lacks certainty.
This extract from Sextus (Hypotyp., bk. 2, c. 9) illustrates many important points: 1. the ancient dogmatists had recognised that all human knowledge can be reduced to a single principle, that is, to a most universal conception, which the sceptics accepted without opposition but of which they contested the certainty; 2. this most universal conception was of SOMETHING, that is, of most common being; 3. knowledge and certainty of knowledge were made to depend simultaneously on this conception of most general being; 4. the sophistry of the sceptics throughout history consists in demanding a demonstration of the ultimate principle, that is, a reason for the final reason, which is a contradiction in terms.
The easy way of refuting the sceptics is to avoid aiding them in their intellectual excess, as they try to demonstrate what is essentially undemonstrable and indeed so evident that from it we can draw the demonstration of every lower truth. We need to show that their system rests on the false supposition that truth is something beyond the ultimate reason or most universal conception. Human beings, when they say they know the truth of a proposition, simply mean that they see the connection between the proposition and the final reason, that is, the most universal conception, totally evident in itself.