<Of the Solidity or Impenetrability of Matter>, showing there is an ambiguity in the meaning of the word solidity, and that Priestley has not succeeded in showing that matter is not solid or impenetrable.Chap.IV.<Of the Inertia of Matter>, showing that Priestley does not follow Newton.The whole is the result of much reading and reflection.".
II <Miscellaneous Reflections on Priestley's account of Hartley's Theory of Me Human Mind>.He shows that Hartley's views were unfounded hypotheses, but speaks with great fondness and respect of Hartley.He is very severe upon Priestley's employment of Hartley's theories, particularly upon his attempt to explain every mental faculty by association.He refers to Aristotle's views of association.
He shows that association cannot account for memory, which was explained by the vividness of the ideas." Every man knows what memory is, and every man knows what is meant by vividness of ideas or conceptions, and their power of suggesting one another; and when we know and understand what each of these things is we can be at no loss to know whether they are one and the same.Let every man judge for himself whether memory is a certain degree {474} of vividness in ideas, and of a certain degree of strength in their power of suggesting one another.To me they appear to be things quite of a different nature; and I could as easily believe that a hat is a pair of shoes as that memory is a certain degree of vividness in ideas and of strength in their association." "Amalefactor that is going to be hanged has a cluster of very vivid ideas, and very strongly associated, of what he is about to suffer, but it is not the object of remembrance but of foresight;" or, "It appears evident, therefore, that something more than association of ideas is required to produce memory, and consequently that association is not of itself sufficient to explain or account for memory." He shows that association cannot account for judgment; "for if there is a power in the mind of comparing ideas and of perceiving certain relations between them, such as those of universal concurrence and perfect coincidence, this power is not that of association; for it is evident that ideas may be associated with any degree of strength without being compared, without perception of any relation between them."He shows in much the same way that association cannot account for the passions and volition.He shows in the same paper that Priestley's attempt to get Locke's ideas of reflection from sensation utterly fails.Priestley had said, "got by abstraction." "We would be glad to be informed by Dr.Priestley whether a man, when he thinks, is not conscious of his thoughts? Whether he has not the power of reflecting upon his own thoughts and making them an object of thought," &c.
III.<On Liberty or Necessity>."The liberty of the will is a phrase similar to that of the liberty of speech.
The last signifies not a power inherent in speech, but a power in the man to speak this or that.In like manner, the liberty of the will signifies not a power inherent in the will, but a power in man to will this or that." "This power is given by his Maker; and, at his pleasure whose gift it is, it may be enlarged or diminished, continued or withdrawn.No power in the creature can be independent of the Creator.The hook is in its nose; he can give it line as far as he sees fit, and when he pleases can restrain it or turn it whither soever he will.Let this be always understood when we ascribe liberty to man or to any created being.Supposing it therefore to be true that man is a free agent, it may be true at the same time that his liberty may be impugned or lost by disorder of body or of mind, as in melancholy or in madness; it may be impaired or lost by vicious habits; it may in particular cases be restrained by divine interposition." He explains cause and effect, native and active power, liberty and necessity, standing up for efficient cause.In a fragmentary paper upon the same subject, perhaps a continuation: "I grant that all rational beings are influenced and ought to be influenced by motives.
But the relation between a motive and the action is of a very different nature from the relation between an efficient cause and its effect.An efficient cause must be a being that exists and has power to produce the effect.A motive is not a thing that exists.It is only a thing conceived in the mind of the agent, and is what the schoolmen called an ens rationis, and therefore cannot possibly be the efficient cause of any thing.It may influence to action, but it cannot act.It is like advice or persuasion, which may have an influence of the same kind with that of motives; but they leave the man still at liberty and indeed suppose liberty.