My Aunt T. was married to a gruff and taciturn Irishman who rejoiced under the name of 'Morris.' Thinking to engage Uncle Mo in conversation during one of my infrequent visits to the Big Apple, and knowing that Morris drove a beer truck, I once made some comment about the superiority of German over American beer. Uncle Mo, not to be seduced into the bracing waters of dialectic, replied, "Beer is beer." End of conversation.
But the beginning of an interesting line of thought. A tautology is a logical truth. To be precise, a tautology is a logical truth within the propositional calculus. (Every tautology is a logical truth, but not every logical truth is a tautology. The logical truths of the predicate calculus are not tautologies, strictly speaking.)
But having no need on the present occasion to be so persnickety, we may use 'tautology' and 'logical truth' interchangeably. Thus it is easy to see why someone would consider 'Beer is beer' and 'Pleasure is pleasure' to be tautologies. They 'say nothing' about the world; they say nothing about anything that might have been different. (Cf. L. Wittgenstein, Tractatus Logico-Philosophicus 4.461 et passim.)
But are they really tautologies? That depends.
Distinguish among sentence-type, sentence-token, and proposition (thought, Fregean Gedanke). The proposition is what is expressed on a given occasion by the tokening of an indicative mood sentence-type. Although the indicative mood English sentence-type 'Beer is beer' can be used (tokened) to express a tautological proposition, it can also be used to express a non-tautological proposition.
Thus in our laconic exchange, Uncle Mo was not attempting to instruct me in a truth of logic. He was out to make a synthetic a posteriori judgment -- a false one in my humble opinion -- which is better rendered by 'All beer is the same in quality' or something like that. So we can say that Morris was using a sentence-type whose surface grammar typically fits it for expressing tautologies to express a non-tautological proposition.
The same goes for 'Pleasure is pleasure' on some occasions of its use. In the context of critique of J. S. Mill's hedonism, the sentence could be used to express the non-tautological proposition that pleasure as such does not furnish a criterion for distinguishing between normatively higher and lower pleasures.
The moral of the story: whether or not a sentence expresses a tautology cannot be decided on the basis of its surface grammar alone. One must consider which proposition the sentence is being used to express, a consideration that demands attention to the context.
This is part of a more general phenomenon. Take a sentence of the form 'a is F.' One would readily classify a sentence of this form as a predication and distinguish it from an existential sentence. But 'God is fictional' has the form in question, yet the latter sentence does not express a predicative proposition: the thought is not that God has the property of being fictional. The thought is rather that God does not exist. Thus a sentence whose surface form is predicative is being used to make a negative existential claim. (Of course, a Meinongian will put up a fight here, but that's another post.)
Other examples of the same phenomenon can be adduced. But in the interests of blogospheric brevity, I cease and desist.
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