How short soever their Knowledge may come of an universal...

How short soever their Knowledge may come of an universal, or perfect Comprehension of whatsoever is, it yet secures their great Concernments, that they have Light enough to lead them to the Knowledge of their Maker, and the sight of their own Duties.

Men may find Matter sufficient to busy their Heads, and employ their Hands with Variety, Delight, and Satisfaction; if they will not boldly quarrel with their own Constitution, and throw away the Blessings their Hands are fill'd with, because they are not big enough to grasp every thing. [Essay I i 5] The pursuit of happiness-the genuine business of human life, on Locke's view-demands only that religion, morality, and science be established to a degree that permits practical progress.

Even with respect to such vital matters, Locke supposed, our knowledge is often limited. The testimony of our senses, together with a natural inclination to seek pleasure and avoid pain, guides much of our daily conduct even though sensitive knowledge cannot offer demonstrative certainty about the existence of an external world. [Essay IV xi 8-10] It would be foolish indeed to refuse to eat simply because God has not granted us speculative certainty regarding the nutritional efficacy of food.

Divine provision for the practical needs of human life is expressed more economically: So in the greatest part of our Concernment, he has afforded us only the twilight, as I may so say, of Probability, suitable, I presume, to that State of Mediocrity and Probationership, he has been pleased to place us in here.

[Essay IV xiv 2] The pace of ordinary life commonly requires all of us to act quickly, on the basis of little more than our fallible memory of the merely probable evidence in favor of this course of action, Locke supposed, but awareness of this common reliance on "our mutual Ignorance" appropriately motivates broad toleration of the diversity of opinions and practices to which others may adhere.

[Essay IV xvi 3-4] The great theme of the Essay, then, is that we ought not to expect to achieve knowledge beyond the relatively narrow confines of what is necessary or, at least, useful for the practical conduct of human life. Although speculative knowledge of the essences of God, human beings, and material things exceeds the capacity of our cognitive faculties, according to Locke, we have no grounds for complaint.