This method could also be called a zero-method. In a logical proposition,
propositions are brought into equilibrium with one another, and the state
of equilibrium then indicates what the logical constitution of these
propositions must be.
6.122 It follows from this that we can actually do without logical
propositions; for in a suitable notation we can in fact recognize the
formal properties of propositions by mere inspection of the propositions
themselves.
6.1221 If, for example, two propositions 'p' and 'q' in the combination 'p
z q' yield a tautology, then it is clear that q follows from p. For
example, we see from the two propositions themselves that 'q' follows from
'p z q . p', but it is also possible to show it in this way: we combine
them to form 'p z q . p :z: q', and then show that this is a tautology.
6.1222 This throws some light on the question why logical propositions
cannot be confirmed by experience any more than they can be refuted by it.
Not only must a proposition of logic be irrefutable by any possible
experience, but it must also be unconfirmable by any possible experience.
6.1223 Now it becomes clear why people have often felt as if it were for us
to 'postulate ' the 'truths of logic'. The reason is that we can postulate
them in so far as we can postulate an adequate notation.
6.1224 It also becomes clear now why logic was called the theory of forms
and of inference.
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