He maintained that visual consciousness is merely a system of arbitrary signs which symbolize for us certain actual or possible tactual experience - in other words a purely conventional language.
The contents of the visual and the tactual consciousness have no element in common.
I recently published a paper on tactual perception, and completed one on visual depth perception.
The visible and visual signs are definitely connected with tactual experiences, and the association between them, which has grown up in our minds through custom or habit, rests upon, or is guaranteed by, the constant conjunction of the two by the will of the Universal Mind.
It was evident that a similar analysis might have been applied to tactual consciousness which does not give externality in its deepest significance any more than the visual; but with deliberate purpose Berkeley at first drew out only one side of his argument.