Full Idea
The Conceptual or Mental distinction is when A and B are actually identical but we have two different ways of conceiving them.
Gist of Idea
Conceptual/Mental distinction: one thing can be conceived of in two different ways
Source
report of Francisco Suárez (Disputationes metaphysicae [1597], Bk VII) by Stephen Boulter - Why Medieval Philosophy Matters 4
Book Reference
Boulter,Stephen: 'Why Medieval Philosophy Matters' [Bloomsbury 2019], p.98
A Reaction
This is the Morning and Evening Star. I bet Frege never read Suarez. This seems to be Spinoza's concept of mind/body.