catechism,
asking people how clearly or how dimly they saw things "in their
mind's eye".

"Think of your breakfast-table," he said; "is your mental picture of
it as clearly illuminated and as complete as your actual view of the
scene?" Mr. Galton began by questioning friends in the scientific
world, F.R.S.'s and other savants. "The earliest results of my
inquiry amazed me. . . . The great majority of the men of science to
whom I first applied, protested that _mental imagery was unknown to
them_, and they looked on me as fanciful and fantastic in supposing
that the words 'mental imagery' really expressed what I believed
everybody supposed them to mean." One gentleman wrote: "It is only
by a figure of speech that I can describe my recollection of a scene
as a 'mental image' which I can 'see' with 'my mind's eye'. I do not
see it," so he seems to have supposed that nobody else did.

When he made inquiries in general society, Mr. Galton found plenty of
people who "saw" mental imagery with every degree of brilliance or
dimness, from "quite comparable to the real object" to "I recollect
the table, but do not see it"--my own position.

Mr. Galton was next "greatly struck by the frequency of the replies in
which my correspondents" (sane and healthy) "described themselves as
subject to 'visions'". These varied in degree, "some were so vivid as
actually to deceive the judgment". Finally, "a notable proportion of
sane persons have had not only visions, but actual hallucinations of
sight at one or more periods of their life. I have a considerable
packet of instances contributed by my personal friends." Thus one
"distinguished authoress" saw "the principal character of one of her
novels glide through the door straight up to her. It was about the
size of a large doll." Another heard unreal music, and opened the
door to hear it better. Another was plagued by voices, which said
"Pray," and so forth.

Thus, on scientific evidence, sane and healthy people may, and "in a
notable proportion _do_, experience hallucinations". That is to say,
they see persons, or hear them, or believe they are touched by them,
or all their senses are equally affected at once, when no such persons
are really present. This kind of thing is always going on, but "when
popular opinion is of a matter-of-fact kind, the seers of visions keep
quiet; they do not like to be thought fanciful or mad, and they hide
their experiences, which only come to