My friend Joel Tay has just posted his interesting seminary essay The Logical Coherency of the Intellectual Triunity of God on his blog here. It is certainly an excellent article [which would be better with better formatting], though I do not think I would agree with [Dr. Gordon H.] Clark's definition of "person" as "a set of thoughts" or "a man is what he thinks". While logic and thinking is indeed necessary, it is not ontologically primary. As Dr. C. Matthew McMahon wrote in his book with regards to the relation of God and logic, The Two Wills of God (New Lenox, IL, USA: Puritan Publications, 2005),
Epistemologically, logic precedes God. Ontologically, God precedes logic (p. 24, footnote 5)
So for man the imago dei, while it is indeed impossible to separate thoughts and reasoning from a person, yet to collapse ontology into epistemology is I think in error. So rather than defining "person" as "a set of thoughts" or "a man is what he thinks", "person" could be better defined as "an entity which thinks" or "a man is an entity formed by what he thinks".