“There is here a feeling, and a conclusion drawn from it, or some way suggested by it.  In order to compare these, we must view them separately, and then consider by what tie they are connected, and wherein they resemble one another.  The hardness of the table is the conclusion, the feeling is the medium by which we are led to that conclusion.  Let a man attend distinctly to this medium, and to the conclusion, and he will perceive them to be as unlike as any two things in nature.  The one is a sensation of the mind, which can have no existence but in a sentient being; nor can it exist one moment longer than it is felt; the other is in the table, and we conclude, without any difficulty, that it was in the table before it was felt, and continues after the feeling is over.  The one implies no kind of extension, nor parts, nor cohesion; the other implies all these.  Both, indeed, admit of degrees, and the feeling, beyond a certain degree, is a species of pain; but adamantine hardness does not imply the least pain.

“And as the feeling hath no similitude to hardness, so neither can our reason perceive the least tie or connection between them; nor will the logician ever be able to show a reason why we should conclude hardness from this feeling, rather than softness, or any other quality whatsoever.  But, in reality, all mankind are led by their constitution to conclude hardness from this feeling.”

It is well worth while to read this extract several times, and to ask oneself what Reid meant to say, and what he actually said.  He is objecting, be it remembered, to the doctrine that the mind perceives immediately only its own ideas or sensations and must infer all else.  His contention is that we perceive external things.

Does he say this?  He says that we have feelings of touch from which we conclude that there is something external; that there is a feeling, “and a conclusion drawn from it, or some way suggested by it;” that “the hardness of the table is the conclusion, and the feeling is the medium by which we are led to the conclusion.”

Could Descartes or Locke have more plainly supported the doctrine of representative perception?  How could Reid imagine he was combatting that doctrine when he wrote thus?  The point in which he differs from them is this:  he maintains that we draw the conclusion in question without any reasoning, and, indeed, in the absence of any conceivable reason why we should draw it.  We do it instinctively; we are led by the constitution of our nature.

In effect Reid says to us:  When you lay your hand on the table, you have a sensation, it is true, but you also know the table is hard.  How do you know it?  I cannot tell you; you simply know it, and cannot help knowing it; and that is the end of the matter.

Reid’s doctrine was not without its effect upon other philosophers.  Among them we must place Sir William Hamilton (1788-1856), whose writings had no little influence upon British philosophy in the last half of the last century.