In one of their arguments against the radical neuron doctrine, Gold & Stoljar (G&S) use the idea that, in certain situations, equivalent terms may not be substitutable into statements that regard properties of the objects to which the terms refer. This device allows G&S to refute the necessity of the conclusion that “the science of the mind equals the science of the brain” even though they take as a premise that the mind equals the brain. I argue, however, that this practice leaves the meaning of the “science of the mind” and the “science of the brain” indeterminate.