Whatever the expositor originally meant, he almost certainly now takes his former statement as couched in elliptical phraseology, and assumes that he was meaning, 'This is a college building and is commodious.' Here the demonstrative phrase or the gesture, which demonstrates the 'it' which is commodious, has now been reduced to 'this'; and the attenuated phrase, under the circumstances in which it is uttered, is sufficient for the purpose of correct demonstration.

This brings out the point that the verbal form is never the whole phraseology of the proposition; this phraseology also includes the general circumstances of its production.

Thus the aim of a demonstrative phrase is to exhibit a definite 'it' as a bare objective for thought; but the _modus operandi_ of a demonstrative phrase is to produce an awareness of the entity as a particular relatum in an auxiliary complex, chosen merely for the sake of the speculative demonstration and irrelevant to the proposition.

For example, in the above dialogue, colleges and buildings, as related to the 'it' speculatively demonstrated by the phrase 'this college building,' set that 'it' in an auxiliary complex which is irrelevant to the proposition 'It is commodious.' Of course in language every phrase is invariably highly elliptical.
Accordingly the sentence 'This college building is commodious' means probably 'This college building is commodious as a college building.' But it will be found that in the above discussion we can replace 'commodious' by 'commodious as a college building' without altering our conclusion; though we can guess that the recipient, who thought he was in the lion-house of the Zoo, would be less likely to assent to.
'Anyhow, it is commodious as a college building.' A more obvious instance of elliptical phraseology arises if the expositor should address the recipient with the remark, 'That criminal is your friend.' The recipient might answer, 'He is my friend and you are insulting.' Here the recipient assumes that the phrase 'That criminal' is elliptical and not merely demonstrative.

In fact, pure demonstration is impossible though it is the ideal of thought.