Positivism

Empiricism

The roots of positivism stretch back as far as the British empiricists of the late 17th and early 18th centuries. The founder of empiricism, John Locke (1632–1704), claimed that rational agents had an ethical duty to arrange their beliefs like a skyscraper. As skyscrapers require a foundation on which their floors stand, beliefs should be stacked up so those on the “upper floor” could be inferable from those on the “lower floor.” Probable reasoning was claimed to suffice for justifying beliefs so long as the chain of justification eventuated in “foundational” beliefs. A belief needed to be intrinsically warranted (i.e., self-justifying) to pass as foundational.

Locke asserted that only beliefs known with certainty should qualify as foundational. He restricted this class of beliefs to those stemming from reflection on self-evident truths or the empirical senses. Self-evident truths included logical relations, such as, “It is either raining or it is not raining.” The empirical senses included taste, touch, smell, sight, and hearing. He considered these two sources of belief to be incorrigible (i.e., not correctable). For instance, a woman can mistake a tree for a person from afar. Yet, close analysis reveals the woman was actually led astray by an inference rather than observation. If the woman had not inferred (i.e., reported observing what appeared to be a person), she would not have needed correction.

Empiricists after Locke developed a psychology to match this bold epistemology. They hypothesized that any conceivable idea, regardless of its complexity, was built up from bundles of sensation. The idea of an apple, for example, was a composite of a variety of taste, visual, and other tactile sensations. The mind constructed the apple-idea by mental operations (e.g., habits of associating sensations). All entertained ideas, except perhaps logical and mathematical ones, originated in the rearrangement of sensations. Thus, an empiricist might say a person born blind could never conceive shades of color.

David Hume (1711–1776) proposed an empiricist test, typically known as “Hume’s fork,” to determine whether a claim was knowable in principle. To implement it, one evaluated whether the claim’s content consisted of ideas that had their ultimate source in pure sensation or reflection. If the claim did, then its truth or falsity was found to be knowable with inquiry. Otherwise, the claim referred to things beyond the limits of human knowledge. The test, of course, assumed an empiricist psychology. The purpose of this test, which later positivists liked, was to distinguish unknowable metaphysical speculation from plausible scientific hypotheses.

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