has also lost the ideas of them; though the organs of speech still retain
somewhat of their usual habits of articulation.

This observation may throw some light on the medical treatment of deaf
people; as it may be learnt from their dreams whether the auditory nerve be
paralytic, or their deafness be owing to some defect of the external organ.

It rarely happens that the immediate organ of vision is perfectly
destroyed. The most frequent causes of blindness are occasioned by defects
of the external organ, as in cataracts and obfuscations of the cornea. But
I have had the opportunity of conversing with two men, who had been some
years blind; one of them had a complete gutta serena, and the other had
lost the whole substance of his eyes. They both told me that they did not
remember to have ever dreamt of visible objects, since the total loss of
their sight.

V. Another method of discovering that our ideas are animal motions of the
organs of sense, is from considering the great analogy they bear to the
motions of the larger muscles of the body. In the following articles it
will appear that they are originally excited into action by the irritation
of external objects like our muscles; are associated together like our
muscular motions; act in similar time with them; are fatigued by continued
exertion like them; and that the organs of sense are subject to
inflammation, numbness, palsy, convulsion, and the defects of old age, in
the same manner as the muscular fibres.

1. All our perceptions or ideas of external objects are universally allowed
to have been originally excited by the stimulus of those external objects;
and it will be shewn in a succeeding section, that it is probable that all
our muscular motions, as well those that are become voluntary as those of