Locke's Externalism about ‘Sensitive Knowledge’

Abstract

Locke characterizes sensitive knowledge as knowledge of the existence of external objects present to the senses, and in terms of an ‘assurance’ that falls short of the certainty of intuition and demonstration. But it is unclear how this fits with his general definition of knowledge, as the perception of the agreement or disagreement of ideas, and it is unclear how that assurance can amount to knowledge, rather than amounting to mere probability (which he contrasts with knowledge). Some contend that Locke does not regard sensitive knowledge as genuine knowledge, but only honourifically calls it knowledge. In contrast, I argue that Locke holds that sensitive knowledge is knowledge, though he takes the conditions for it to be very different from the conditions for intuitive and demonstrative knowledge. It is not the assurance alone which Locke thinks qualifies sensitive knowledge as such: it is also the fact that the assurance arises from the actual employment of the senses upon external objects, and the fact that the senses do not generally deceive us, which he thinks qualifies sensitive knowledge as genuine knowledge. That there is a (tacit) form of externalism in Locke's account of sensitive knowledge is the main thesis of this paper.

Keywords:

• Locke
• knowledge
• externalism
• assurance

Notes

¹Unless otherwise noted, all references to Locke are from the An Essay Concerning Human Understanding (1689), the P. H. Nidditch edition (Oxford, 1975). References provide the book, chapter, and section of the relevant passage(s), along with the page numbers in the Nidditch edition.

²For instance, BonJour (‘Externalist Theories’) writes:

When viewed from the general standpoint of the western epistemological tradition, externalism represents a very radical departure. It seems safe to say that until very recent times, no serious philosopher of knowledge would have dreamed of suggesting that a person's beliefs might be epistemically justified simply in virtue of facts or relations that were external to his subjective conception. (56)

³Commentators have taken such passages to indicate that, on Locke's view, certainty is necessary for all knowledge. Newman writes: ‘Locke is in a tradition that reserves knowledge-talk for what we're certain of, as opposed to what we think probable. He holds that certainty “is requisite to Knowledge”; that “to know, and be certain, is the same thing” (‘Locke on Knowledge’, 316). Newman claims that, according to Locke, ‘[a]ll knowledge is marked by perceptual certainty’ (322), though he notes that ‘[n]ot all certainty is achieved via the same route’ (ibid.).

⁴See IV.xi.9: 635–6, quoted earlier.

⁵Owen makes essentially the same claim about Locke's use of ‘assurance’; Owen writes: ‘there are just too many other uses of the term “assurance”, as a generic term for either knowledge or belief, for it to be plausible to claim that “assurance” is a technical term reserved for belief or probability’ ('Sensitive Knowledge’, 9).

⁶Even further evidence that Locke thinks of sensitive knowledge as genuine knowledge is where he says:

If general knowledge, as has been shown, consists the Perception of the Agreement, or Disagreement of our own Ideas; and the Knowledge of the existence of all Things without us (except only of a GOD whose existence every Man may certainly know and demonstrate to himself from his own existence) be had only by Senses; What room then is there for the Exercise of any other Faculty, but outward Sense and inward Perception. (IV.xvii.2: 668)

Moreover, in reference to sensitive knowledge, he writes: ‘But this Knowledge extends as far as the present Testimony of our Senses, employ'd about particular Objects, that do then affect them, and no farther’ (IV.xi.9). Here, again, Locke refers to sensitive knowledge as knowledge without giving any qualification of his use of ‘knowledge’.

⁷For instance, Hill (‘Locke's Definition’) argues that knowledge of external things is secured by the fact that the ideas perceived to agree denote external things, and that this denotation is the ground for the truth of the perceived agreement. Mattern (‘Locke: Our Knowledge’) makes clear that, on Locke's view, the perception of an agreement of ideas is the perception of a true proposition. Also, see Allen (‘Locke on Sensitive Knowledge’).

⁸As Allen observes, ‘[c]entral to Locke's account of sensitive knowledge is a distinction between having and receiving ideas’ (‘Locke on Sensitive Knowledge’, 256).

⁹In contrast, Owen ('Sensitive Knowledge’, 7) has the same interpretation as I do regarding the exact ideas that enter into sensitive knowledge.

¹⁰Nagel (‘Locke on Skepticism’, 23) and Rickless (‘Knowledge or Assurance’, 40) support Allen's interpretation.

¹¹Nagel (‘Locke on Skepticism’, 23) points this out, but claims that ‘Locke's meaning is clearly the second’.

¹²Oxford English Dictionary Online, entry for ‘whereof, adv.’; accessed January 2014.