Conatus: REVISED EDITION by Tom Wallace - HTML preview

C O N A T U S

then the argument is valid. When, in addition, the premises are true, the argument is sound. But notice that the conclusion, ‘B is white’, is actually only possibly true. This was the issue that was raised earlier — even if an absolute necessary truth could be discovered it does not mean that any conclusion that can be drawn from it must also be necessary. There are, after all, black swans.

The swans illustrations above are typical examples given of logic based on Aristotle’s three laws of logic. Aristotle’s three laws have been defined as:

The principle of identity (A is A). The principle of non-contradiction (not both A and not-A).

The principle of the excluded middle (either A or not-A).

The last two principles are arguably equivalent.

To get a better feel for the logic may however be useful. How about this example from Bertrand Russell — the queen of America is bald. Or how about — unicorns are vicious? It’s helpful to re-frame these in the manner of the earlier examples. Hence, for unicorns:

There exists a creature called a unicorn. All encounters with unicorns suggest that they are aggressive and uncooperative. Therefore, it’s true to say, all unicorns are vicious.

Now we have premises and a conclusion that can be analysed. Again, of course, this is a trivial example. It’s easy to say that unicorns

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