William Kingdon Clifford, answered from the texts and cited to the page.
That which is the reality underlying the appearance we call matter is mind-stuff: elementary feelings which stand to consciousness as the molecules of a body stand to the body.12 The material world is how mind-stuff appears to another mind.34
Hence a feeling (or an eject-element) is Ding-an-sich, an absolute, whose existence is not relative to anything else. Sentitur is all that can be said. 2. These eject-elements, which correspond to motions of matter, are connected together in their sequence and co-existence by counterparts of the physical laws of ON THE NATURE OF THINGS-IN-THEMSELVES. 85 matter. For otherwise the correspondence could not be kept up.Lectures and Essays Vol II, ed. Pollock
Matter and the sensible universe are the relations between particular organisms, that is, mind organized into consciousness, and the rest of the world. This leads to results which would in a loose and popular sense be called materiahst. But the theory must, as a metaphysical theory, be reckoned on the ideahst side. To speak technically, it is an idealist monism.Lectures and Essays Vol I, ed. Pollock with memoir
As we go back along the line, the complexity of the organism and of its nerve-action insensibly diminishes; and for the first part of our course we see reason to think that the com- plexity of consciousness insensibly diminishes also. But if we make a jump, say to the tunicate molluscs, we see no reason there to infer the existence of consciousness at all.Lectures and Essays Vol II, ed. Pollock
The cerebral image is an imperfect representation of tlie candlestick, corresponding to it point for point in a certain way. Both the candlestick and the cerebral image are matter; but one material complex represents the other material complex in an imperfect way. Now the candlestick is not the external reahty whose existence is represented in the man's mind; for the candlestick is a mere perception in my mind.Lectures and Essays Vol II, ed. Pollock
Dismissed for a century and now cited as an anticipation of contemporary panpsychism.