Abstract

In his fascinating and provocative paper, "Sharp Boundaries for Blobs," Roy Sorensen gives several arguments against the possibility of "vague objects," or objects with indeterminate boundaries.1 In what follows, I will examine the main argument given by Sorensen in his paper. This argument has a great deal of initial plausibility. Moreover, I happen to sympathize with its conclusion. Nevertheless, it seems to me that Sorensen's argument fails to establish that conclusion. The purpose of this paper is to show why. I will argue that, upon careful examination, it can be seen that Sorensen's argument involves a fatal equivocation. Sorensen's argument is based on a kind of thought experiment. We are asked to consider, as a paradigm example of a vague object, a grey sphere (also known as "the blob") that fades into a white background. And we are asked to imagine a spherical cavity growing from the center of the blob, so that the growth of the cavity eventually destroys the blob. Sorensen's argument, which is explicitly spelled out in Section I of his paper, goes like this: 1. The blob must have a boundary. 2. If a spherical cavity grows from the center of the blob, the blob's outer boundary is completely unaffected as long as some of the blob remains. 3. As soon as nothing remains of the blob, the blob's boundary goes out of existence all at once.