Attention to specific issues at hand often leads us to...

Attention to specific issues at hand often leads us to overlook the function of the most noble of our faculties, but Locke believed that the operations of the human understanding are familiar to us all. We employ ourselves in thinking, deciding, doing, and knowing all the time. What we require is not a detailed scientific explanation of the nature of the human mind, but rather a functional account of its operations in practice.

For that purpose, Locke supposed, we must pursue the "Historical, plain Method" of observing ourselves in the process of thinking and acting. With respect to each significant area of human knowledge, we must ask ourselves: where does it come from, how reliable is it, and how broadly does it extend? [Essay I i 1-2] The last of these questions is arguably most to the point.

Locke realized early on in his epistemological reflections that skeptical doubts often arise from unreasonable expectations about the degree of certainty it is possible for us to attain. [King, p. 107] Academic philosophers have contributed to the problem by demanding demonstrative certainty of the speculative truth even in instances where we are unlikely to be able to achieve it.

But their demands for excessive precision in philosophical language lead only to pointless wrangling over the meanings of their terms, on Locke's view. The simple truth is that we can't be certain about everything, and it would be counter-productive to try to expand our knowledge beyond its natural limits. Since we are not capable of knowing everything, contentment with our condition requires a willingness not to reach beyond the limitations of our cognitive capacities.

Our intellectual energy would be most efficiently employed were we to avoid intractable disputes over matters beyond our ken and rely instead upon our "Satisfaction in a quiet and secure Possession of Truths, that most concern'd us." [Essay I i 7] In ordinary life, we know what we need to know, and expecting more than that would only lead us to despair. The Great Concernments After all, Locke argued, we do have what we need most.

The practical conduct of human life doesn't depend upon achieving speculative certainty about the inner workings of the natural world or acquiring detailed information about our own natures. It will be enough if we can secure "the Conveniences of Life" and recognize what we ought to do.