SECT。1 Moral Distinctions Not Derived from Reason
There is an inconvenience which attends all abstruse reasoning，that it may si-lence，without convincing an antagonist，and requires the same intense study to make us sensible of its force，that was at first requisite for its invention。When we leave our clos-et，and engage in the common affairs of life，its conclusions seem to vanish，like the phantoms of the night on the appearance of the morning；and it is difficult for us to re-tain even that conviction，which we had attained with difficulty。This is still more con-spicuous in a long chain of reasoning，where we must preserve to the end the evidence of the first propositions，and where we often lose sight of all the most received maxims，ei-ther of philosophy or common life。I am not，however，without hopes，that the present system of philosophy will acquire new force as it advances；and that our reasonings con-cerning morals will corroborate whatever has been said concerning the understanding and the passions。Morality is a subject that interests us above all others：We fancy the peace of society to be at stake in every decision concerning it；and it is evident，that this con-cern must make our speculations appear more real and solid，than where the subject is，in a great measure，indifferent to us。What affects us，we conclude can never be a chi-mera；and as our passion is engaged on the one side or the other，we naturally think that the question lies within human comprehension；which，in other cases of this nature，we are apt to entertain some doubt of。Without this advantage I never should have ventured upon a third volume of such abstruse philosophy，in an age，wherein the greatest part of men seem agreed to convert reading into an amusement，and to reject every thing that requires any considerable degree of attention to be comprehended。
It has been observed，that nothing is ever present to the mind but its perceptions；and that all the actions of seeing，hearing，judging，loving，hating，and thinking，fall under this denomination。The mind can never exert itself in any action，which we maynot comprehend under the term of perception；and consequently that term is no less ap-plicable to those judgments，by which we distinguish moral good and evil，than to every other operation of the mind。To approve of one character，to condemn another，are only so many different perceptions。
Now as perceptions resolve themselves into two kinds，viz。impressions and ideas，this distinction gives rise to a question，with which we shall open up our present enquiry concerning morals。Whether it is by meants of our ideas or impressions we distinguish betwixt vice and vertue，and pronounce an action blameable or praiseworth？This will immediately cut off all loose discourses and declamations，and reduce us to something precise and exact on the present subject。
Those who affirm that virtue is nothing but a conformity to reason；that there are e-ternal fitnesses and unfitnesses of things，which are the same to every rational being that considers them；that the immutable measures of right and wrong impose an obligation，not only on human creatures，but also on the Deity himself：All these systems concur in the opinion，that morality，like truth，is discerned merely by ideas，and by their juxta-position and comparison。In order，therefore，to judge of these systems，we need only consider，whether it be possible，from reason alone，to distinguish betwixt moral good and evil，or whether there must concur some other principles to enable us to make that distinction。
If morality had naturally no influence on human passions and actions，it were in vain to take such pains to inculcate it；and nothing would be more fruitless than that multitude of rules and precepts，with which all moralists abound。Philosophy is com-monly divided into speculative and practical；and as morality is always comprehended under the latter division，it is supposed to influence our passions and actions，and to go beyond the calm and indolent judgments of the understanding。And this is confirmed by common experience，which informs us，that men are often governed by their duties，and are detered from some actions by the opinion of injustice，and impelled to others by that of obligation。
Since morals，therefore，have an influence on the actions and affections，it fol-lows，that they cannot be derived from reason；and that because reason alone，as we have already proved，can never have any such influence。Morals excite passions，and produce or prevent actions。Reason of itself is utterly impotent in this particular。The rules of morality。therefore，are not conclusions of our reason。
No one，I believe，will deny the justness of this inference；nor is there any other means of evading it，than by denying that principle，on which it is founded。As long as it is allowed，that reason has no influence on our passions and action，it is in vain to pretend，that morality is discovered only by a deduction of reason。An active principle can never be founded on an inactive；and if reason be inactive in itself，it must remain so in all its shapes and appearances，whether it exerts itself in natural or moral subjects，whether it considers the powers of external bodies，or the actions of rational beings。
It would be tedious to repeat all the arguments，by which I have proved，that rea-son is perfectly inert，and can never either prevent or produce any action or affection。it will be easy to recollect what has been said upon that subject。I shall only recall on this occasion one of these arguments，which I shall endeavour to render still more conclu-sive，and more applicable to the present subject。
Reason is the discovery of truth or falshood。Truth or falshood consists in an agree-ment or disagreement either to the real relations of ideas，or to real existence and matter of fact。Whatever，therefore，is not susceptible of this agreement or disagreement，is in-capable of being true or false，and can never be an object of our reason。Now it is evi-dent our passions，volitions，and actions，are not susceptible of any such agreement or disagreement；being original facts and realities，compleat in themselves，and implying no reference to other passions，volitions，and actions。It is impossible，therefore，they can be pronounced either true or false，and be either contrary or conformable to reason。