Every Man being conscious to himself, That he thinks, and that which his Mind is employ'd about whilst thinking, being the Ideas, that are there, 'tis past doubt, that Men have in their Minds several Ideas, such as are those expressed by the words, Whiteness, Hardness, Sweetness, Thinking, Motion, Man, Elephant, Army, Drunkenness, and others: It is in the first place then to be inquired, How he comes by them? I know it is a received Doctrine, That Men have native Ideas, and original Characters stamped upon their Minds, in their very first Being.
John LockeMathematical proofs, like diamonds, are hard and clear, and will be touched with nothing but strict reasoning.
John LockeFirmness or stiffness of the mind is not from adherence to truth, but submission to prejudice.
John LockeA young man before he leaves the shelter of his father's house, and the guard of a tutor, should be fortify'd with resolution, and made acquainted with men, to secure his virtues, lest he should be led into some ruinous course, or fatal precipice, before he is sufficiently acquainted with the dangers of conversation, and his steadiness enough not to yield to every temptation.
John LockeWhere danger shews it self, apprehension cannot, without stupidity, be wanting; where danger is, sense of danger should be; and so much fear as should keep us awake, and excite our attention, industry, and vigour; but not to disturb the calm use of our reason, nor hinder the execution of what that dictates.
John Locke