 The simplest way to introduce the Via Negativa is to interpret it as a definition of the notion a physical property something like this: F is a physical property if and only if F is a non-mental property. But there are many reasons to resist such a definition. Take vitalism. Vitalism isn’t true, but it might have been true; there is no contradiction in it for example. So imagine a world in which plants and animals instantiate the key property associated with vitalism, viz., élan vital. It seems reasonable to say that in that case plants and animals instantiate a property that is non-physical, i.e. élan vital is not physical. And yet one should not say on this account that plants and animals instantiate a mental property, i.e., élan vital is not mental. In short, élan vital is neither mental nor physical. But the Via Negativa as stated cannot accommodate that fact.