This is all I have to say about the difficulty of having two discrepant concepts together, and about the number of things to which we can simultaneously attend.
THE VARIETIES OF ATTENTION.
The things to which we attend are said to interest us. Our interest in them is supposed to be the cause of our attending. What makes an object interesting we shall see presently; and later inquire in what sense interest may cause attention. Meanwhile
Attention may be divided into kinds in various ways. It is either to
a) Objects of sense (sensorial attention); or to
b) Ideal or represented objects (intellectual attention). It is either
c) Immediate; or
d) Derived: immediate, when the topic or stimulus is interesting in itself, without relation to anything else; derived, when it owes its interest to association with some other immediately interesting thing. What I call derived attention has been named 'apperceptive' attention. Furthermore, Attention may be either
e) Passive, reflex, non-voluntary, effortless; or
f) Active and voluntary.