_Secondly_, We may conclude from the same principle, that the sense of justice is not founded on reason, or on the discovery of certain connexions and relations of ideas, which are eternal, immutable, and universally obligatory. For since it is confessed, that such an alteration as that above-mentioned, in the temper and circumstances of mankind, would entirely alter our duties and obligations, 'tis necessary upon the common system, _that the sense of virtue is derived from reason_, to show the change which this must produce in the relations and ideas. But 'tis evident, that the only cause why the extensive generosity of man, and the perfect abundance of every thing, would destroy the very idea of justice, is, because they render it useless; and that, on the other hand, his confined benevolence, and his necessitous condition, give rise to that virtue, only by making it requisite to the public interest, and to that of every individual. 'Twas therefore a concern for our own and the public interest which made us establish the laws of justice; and nothing can be more certain, than that it is not any relation of ideas which gives us this concern, but our impressions and sentiments, without which every thing in nature is perfectly indifferent to us, and can never in the least affect us. The sense of justice, therefore, is not founded on our ideas, but on our impressions. _Thirdly_, We may farther confirm the foregoing proposition, _that those impressions, which give rise to this sense of justice, are not natural to the mind of man, but arise from artifice and human conventions_. For, since any considerable alteration of temper and circumstances destroys equally justice and injustice; and since such an alteration has an effect only by changing our own and the public interest, it follows, that the first establishment of the rules of justice depends on these different interests. But if men pursued the public interest naturally, and with a hearty affection, they would never have dreamed of restraining each other by these rules; and if they pursued their own interest, without any precaution, they would run headlong into every kind of injustice and violence. These rules, therefore, are artificial, and seek their end in an oblique and indirect manner; nor is the interest which gives rise to them of a kind that could be pursued by the natural and inartificial passions of men.