His metaphysical principles especially appear in his "Discourse on Natural Theology," prefixed to his edition of Paley a work executed when he held the Great Seal of England.This discourse professes to be logical, but does not throw much light on the method of inquiry, or on the nexus of the parts of the theistic argument.He professes to proceed throughout on the method of Bacon, of whom he entertained, as all the Scottish metaphysicians did, a high admiration.He maintains that natural theology " is strictly a branch of inductive theology, formed and supported by the same kind of reasoning upon which the physical and psychological sciences are founded." He argues that " the two inquiries, that into the nature and constitution of the universe and that into the evidence of design which it displays, are to a large extent identical." Turning to psychology, he expresses his wonder that writers in modern times have confined themselves to the proofs afforded by the visible and sensible works of nature, while the evidence furnished by the mind and its operations has been neglected.
" The structure of the mind, in every way in which we can regard it, affords evidence of the most skilful contrivance.
All that adapts it so admirably to the operations which it performs, all its faculties, are plainly means working to an end." He refers in proof to the processes involved in reasoning, association, habit, memory, and to the feelings and affections so adapted to their end.In speaking of habit, he gives a powerful description of what no doubt was his own experience as a speaker." A practised orator will declaim in measured and in various periods; will weave his discourse into one texture; form parentheses within parentheses; excite the passions or move to laughter; take a turn in his discourse from an accidental interruption, making it the topic of his rhetoric for five minutes to come, and pursuing in like manner the new illustrations to which it gives rise; mould his diction with a view to attain or to shun an epigrammatic point, or an alliteration, or a discord; and all this with so much assured reliance on his own powers, and with such perfect ease to himself, that be will even plan the next sentence while he is pronouncing off-hand the one be is engaged with, adapting each to the other, and shall look forward to the topic which is to follow, and fit in the close of the one he is handling to be its introducer; nor will any auditor be able to discover the least difference between all this and the portion of his speech he has got by heart or mark the transition from the one to the other." I do believe that there is proof of design in the structure of a mind that is capable of bringing forth such products; but to ascribe all this to habit while there are a great many other principles involved, argues a defective power of mental analysis on the part of our author.He thinks to the ordinary argument an addition of great importance remains to be made." The whole reasoning proceeds necessarily upon the assumption that there exists a being or thing separate from and independent of matter and conscious of its own existence, which we call mind." So he sets him self against materialism.
He sets no great value on the argument <a priori>, and examines it, not very powerfully, in the form in which it is put by Clarke.He admits, how ever, that, after we have, by the argument <a posteriori>, "satisfied ourselves {364} of the existence of the intelligent cause, we naturally connect with this cause those impressions which we have derived from the contemplation of infinite space and endless duration, and hence we clothe with the attributes of immensity and eternity the awful Being whose existence has been proved by a more vigorous process of investigation." Brougham, it is evident, was ignorant of the terrible criticism to which the theistic argument bad been subjected half a century before by Kant, with whose philosophy he seems to have been utterly unacquainted.He does not see clearly what Kant bad proven, that the <a priori> principle of cause and effect is involved in the argument from design.We look on design as an effect, and infer a designer as a cause, on the principle that every effect has a cause.At the same time he treats of cause and effect." Whence do we derive it? I apprehend only from our consciousness.We feel that we have a will and a power; that we can move a limb.and effect, by our own powers excited after our own volition, a change upon external objects.Now from this consciousness we derive the idea of power, and we transfer this idea and the relation on which it is founded, between our own will and the change produced, to the relations between events wholly external to ourselves, assuming them to be connected as we feel our volition and our movements are mutually connected.If it be said that this idea by no means involves that of necessary connection, nothing can be more certain.The whole is a question of fact, -- of contingent truth." This statement is exposed to criticism.Whence this transference of what we feel, or rather the legitimate application of it, to the objective world? If there be not a necessary principle involved, how are we entitled to argue that world-making, of which we have no experience, implies a world-maker.He argues in behalf of the immortality of the soul, and that it is quite possible to prove a miracle.It has to be added that be has some papers on instinct, on which he throws no great light as he had not caught the idea that instinct is the beginning of intelligence, and that it is capable, within a limited degree, of being cultivated and made hereditary.