Logic of the Mind

Logic of the Mind

Modern logic employs an apparatus of quantifiers and variables. The variables are assigned a domain consisting of discrete individual objects such as dogs and houses—substances, in traditional terminology. Logical laws are formulated against the backdrop of this conception—an ontological conception. Logic is thus tied to an ontology of substances, in particular material substances. Logical necessity is defined by reference to such an ontology. What else could constitute the domain over which we quantify? We need an ontology to form the domain of quantification. No ontology, no logic. But does this ontology apply to the mind? What domain are we quantifying over? As I have argued elsewhere, there is no substance-accident ontology of the mind, or even event ontology.[1] There is no mental counterpart to the ontology of material objects in space. So, we cannot define logical truth with respect to the mind by reference to such an ontology. That would be fine if logical truth did not apply to the mind, but it does. We can use “all” and “some” about the mind and state logical truths, but there is no domain of quantification of the kind commonly presupposed. The situation is analogous to the logic of stuffs: we can speak of “some milk” and “all coal” and say “no milk is coal”, but it is doubtful that such locutions can be paraphrased by reference to glasses of milk and pieces of coal. A fortioriwe can’t paraphrase quantified statements about consciousness by reference to chunks of consciousness or lumps of experience. For example, you can say “All pain is worse than any pleasure” without supposing that pain and pleasure form a domain of objects: there need not be a value of a variable that ranges over a set of objects. Nor do we have to suppose a well-defined domain of selves or persons to accommodate “I am not you” or “Everyone is someone”. Logic as such is not committed to a specific type of ontology—essentially an ontology of substances. Modern logic was formulated with such an ontology in mind, forgetting that not all logical truths concern such an ontology. It follows that this formulation is inadequate to capture the full range of cases. The syntax and semantics of modern logical symbolism is too narrow to do justice to logic in general. The very idea of a variable comes under suspicion of ontological bias. It is typically explained by reference to ordinary material objects without a thought to other sorts of ontology or the lack thereof.[2] The operative notion of a domain is too restricted. Modern logic does not apply to the logic of mind, as mereological logic does not.

[1] See my “Ontology of Mind”.

[2] Another problem case is truths about fictional objects: such objects don’t exist to form a domain. And this is the very reason that many logicians don’t like quantifying over properties. If all quantification is “objectual”, how do we explain quantifying over non-objectual things?