[Essay IV ii 9-10] But Locke supposed that we may be capable...

[Essay IV ii 9-10] But Locke supposed that we may be capable of demonstrative knowledge of moral relations as well, provided that we take care in the formation of abstract ideas of the mixed modes of human action. Our only demonstrative knowledge of real existence, he supposed, is that we can have with respect to God.

[Essay IV x] Although only intuition and demonstration offer certain knowledge of general truths, Locke supposed that sensitive knowledge provides some evidence of the existence of particular objects outside ourselves.

Although it is not always true that there must exist an external object corresponding to each of our ideas of sensation, Locke argued that veracious cases are different enough from illusory cases to warrant an inference to the real existence of their objects, especially when the accompanying perception of pleasure or pain serves as a reliable guide to the practical conduct of human life.

[Essay IV ii 14] Locke had serious reservations about the reliability of our sensitive knowledge of the natural world, and we'll return later to the chapter of the Essay he devoted entirely to an analysis of its difficulties. [Essay IV xi] ©1999-2002 Garth Kemerling.Last modified 27 October 2001.Questions, comments, and suggestions may be sent to: the Contact Page.

The Limits of Knowledge One of the most basic themes of Locke's epistemology is that since we cannot know everything, we would be well-advised to observe and respect the extent and limitations of human knowledge. Given the basic definition of knowledge as perception of the agreement of our ideas, it follows that we fall short of knowing whenever we lack ideas or fail to perceive their agreement.

Thus, intuition extendes only to the identiy and diversity of ideas we already have; demonstration extends only to ideas between which we are able to discover intermediaries; and sensitive knowledge informs us only of the present existence of causes for our sensory ideas. [Essay IV iii 3-5] Awareness of our limitations, Locke proposed, should forestall haste, laziness, and despair in our natural search for the truth about the most vital issues into which human knowers can fruitfully inquire.

[Conduct 39-43] Severe Restrictions Applying the human faculty of reason to the pursuit of knowledge, properly defined, reveals the limitiations within which we must work: We cannot achieve knowledge of things-such as infinity or substantial real essences-for which we lack clear, positive ideas.