Identical, a.
Etymology: [Cf. F. identique. See Identity.]
1. The same; the selfsame; the very same; not different; as, the identical person or thing. I can not remember a thing that happened a year ago, without a conviction . . . that I, the same identical person who now remember that event, did then exist. Reid.
2. Uttering sameness or the same truth; expressing in the predicate what is given, or obviously implied, in the subject; tautological. When you say body is solid, I say that you make an identical proposition, because it is impossible to have the idea of body without that of solidity. Fleming. Identical equation (Alg.), an equation which is true for all values of the algebraic symbols which enter into it.
Shades of meaning
Fernald has no entry of its own for identical; he lists it under alike, synonymous.
Where he writes about it:
An identical proposition is one that says the same thing precisely in subject and predicate. — from alike
To say "this is the identical man," is to say not merely that he is similar to the one I have in mind, but that he is the very same person. — from alike
Synonymous (Gr. syn, together, and onyma, name) strictly signifies being interchangeable names for the same thing, or being one of two or more interchangeable names for the same thing; to say that two words are synonymous is strictly to say they are alike, equivalent, identical, or the same in meaning; but the use of synonymous in this strict sense is somewhat rare, and rather with reference to statements than to words. — from synonymous
H. W. BEECHER Royal Truths p. 294. [T. & F. '66.] In the strictest sense, synonymous words scarcely exist; rarely, if ever, are any two words in any language equivalent or identical in meaning; where a difference in meaning can not easily be shown, a difference in usage commonly exists, so that the words are not interchangeable. — from synonymous
To consider synonymous words identical is fatal to accuracy; to forget that they are similar, to some extent equivalent, and sometimes interchangeable, is destructive of freedom and variety. — from synonymous