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. This practical impossibility of pure
demonstration is a difficulty which arises in the communication of
thought and in the retention of thought. Namely, a proposition about a
particular factor in nature can neither be expressed to others nor
retained for repeated consideration without the aid of auxiliary
complexes which are irrelevant to it.

I now pass to descriptive phrases. The expositor says,

'A college in Regent's Park is commodious.'

The recipient knows Regent's Park well. The phrase 'A college in
Regent's Park' is descriptive for him. If its phraseology is not
elliptical, which in ordinary life it certainly will be in some way or
other, this proposition simply means,

'There is an entity which is a college building in Regent's Park
and is commodious.'

If the recipient rejoins,

'The lion-house in the Zoo is the only commodious building in
Regent's Park,'

he now contradicts the expositor, on the assumption that a lion-house in
a Zoo is not a college building.

Thus whereas in the first dialogue the recipient merely quarrelled with
the expositor without contradicting him, in this dialogue he contradicts
him. Thus a descriptive phrase is part of the proposition which it helps
to express, whereas a demonstrative phrase is not part of the
proposition which it helps to express.

Again the expositor might be standing in Green Park--where there are no
college buildings--and say,

'This college building is commodious.'

Probably no proposition will be received by the recipient because the
demonstrative phrase,

'This college building'

has failed to demonstrate owing to the absence of the background of
sense-awareness which it presupposes.

But if the expositor had said,

'A college building in Green Park is commodious,'

the recipient would have received a proposition, but a false one.

Language is usually ambiguous and it is rash to make general assertions
as to its meanings. But phrases which commence with 'this' or 'that' are
usually demonstrative, whereas phrases which commence with 'the' or 'a'
are often