Abstract
In the _New Theory of Vision, Berkeley defends the heterogeneity thesis, i.e., the view that the ideas of sight and touch are numerically and specifically distinct. In sections 121-122 of that work, he suggests that the thesis of abstract ideas is somehow closely connected to the heterogeneity thesis, though he does not there fully explain just what the connection is supposed to be. In this paper an interpretation of this connection is proposed and defended. Berkeley needs to reject abstract ideas because, if there were such ideas then the heterogeneity thesis would be false and, in turn, this would lead directly to the falsity of Berkeley's theory of vision.