Øystein Linnebo's Thin Objects is an excellent book, full of good ideas and arguments, presented with exemplary clarity. As the title indicates, the book seeks to defend the idea that some objects are metaphysically thin in that their existence makes no substantial demands on the world. Much of the book is devoted to spelling out this philosophical idea in a new way, and to show that mathematical objects such as numbers and sets are thin in the way described. Central to Linnebo's defense of thin objects is the view that it is sufficient for objects of a given kind K to exist that a certain minimal requirement is satisfied: that K-terms occur in true sentences of the right kind and are supplied with a suitable (predicative) criterion of identity.
The book is primarily a contribution to the philosophy of mathematics, given its focus on mathematical objects. But given that the...
