David Hume

The life of man is of no greater importance to the universe than that of an oyster.
On Suicide
He is happy, whose circumstances suit his temper; but he is more excellent, who can suit his temper to any circumstances.
An Enquiry Concerning the Principles of Morals
In our reasonings concerning matter of fact, there are all imaginable degrees of assurance, from the highest certainty to the lowest species of moral evidence. A wise man, therefore, proportions his belief to the evidence.
An Enquiry Concerning Human Understanding
Though experience be our only guide in reasoning concerning matters of fact; it must be acknowledged, that this guide is not altogether infallible, but in some cases is apt to lead us into errors.
An Enquiry Concerning Human Understanding
Nothing appears more surprising to those, who consider human affairs with a philosophical eye, than the easiness with which the many are governed by the few; and the implicit submission, with which men resign their own sentiments and passions to those of their rulers.
Essays, Moral, Political, and Literary
Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.
A Treatise of Human Nature
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.
A Treatise of Human Nature
Generally speaking, the errors in religion are dangerous; those in philosophy only ridiculous.
A Treatise of Human Nature
Be a philosopher; but, amidst all your philosophy, be still a man.
A Treatise of Human Nature