About those messages and the ideas raised in his mind by them he might reason and draw his inferences; and his conclusions would be correct--for what?
For the world of telephonic messages, for the type of messages that go through the telephone.

Something definite and valuable he might know with regard to the spheres of action and of thought of his telephonic subscribers, but outside those spheres he could have no experience.

Pent up in his office he could never have seen or touched even a telephonic subscriber _in himself_.

Very much in the position of such a telephone clerk is the conscious _ego_ of each one of us seated at the brain terminals of the sensory nerves.
Not a step nearer than those terminals can the _ego_ get to the 'outer world,' and what in and for themselves are the subscribers to its nerve exchange it has no means of ascertaining.

Messages in the form of sense-impressions come flowing in from that 'outside world,' and these we analyze, classify, store up, and reason about.