Full Idea
Attributes should not be thought of as identifiable objects. It is better to follow Frege and compare them to mathematical functions. 'Square of' and 'double of' x are distinct functions, even though they are not distinguishable in thought when x is 2.
Gist of Idea
Attributes are functions, not objects; this distinguishes 'square of 2' from 'double of 2'
Source
Peter Geach (Mental Acts: their content and their objects [1957], §11)
Book Reference
Geach,Peter: 'Mental Acts: Their content and their objects' [RKP 1971], p.39
A Reaction
Attributes are features of the world, of which animals are well aware, and the mathematical model is dubious when dealing with physical properties. The route to arriving at 2 is not the same concept as 2. There are many roads to Rome.