I propose to discuss William P. Alston's classic 1958 essay, “Ontological Commitments.”

Philosophers, analytical philosophers at any rate, often engage in the practice of replacing sentences with paraphrases of those sentences. Alston's topic in “Ontological Commitments” is one special case of this practice – the case in which the original sentence is an explicitly existential sentence and the paraphrase is not. In such cases, Alston calls the paraphrase an “ontological reduction” of the original. Here is a well-known example of an ontological reduction – although it belongs to a later chapter in the history of analytical philosophy than Alston's essay:

“Ontological Commitments” is devoted to a question about ontological reductions: what is the point of formulating them – what does the philosopher who “paraphrases away” occurrences of explicitly existential vocabulary mean to accomplish? In the closing paragraphs of the essay he gives his own answer to this question. The body of the essay, however, is devoted to the refutation of a popular answer – perhaps the standard answer – to the question. And the popular or standard answer is this: the ontological reduction of an explicitly existential sentence enables those who endorse the reduction to avoid ontological commitment to entities of the sort asserted to exist by the original, unreduced sentence. In the case of our example: by replacing ‘There are three holes in this piece of cheese’ with ‘This piece of cheese is triply perforate’ we go at least some way toward avoiding ontological commitment both to holes in pieces of cheese and holes in general. (Of course to succeed fully in avoiding ontological commitment to holes, or even holes in pieces of cheese, we should no doubt have to find ontological reductions of many other sentences than that one – ‘There are exactly as many holes in that piece of cheese as there are crackers on that plate’, for example.)