The Issue of The Untrustworthiness of the Senses

Don just to alleviate the concern you just posted about, how about change the thread title to something like "The Issue of The Untrustworthiness of the Senses" which will make it less likely for someone reading the topics to think you are advocating a Skeptical view of that.

I recommend reading the academic book

Pleasure, Mind, and Soul, Selected Papers in Ancient Philosophy by C. C. W. Taylor

The second chapter examines the Epicurean thesis that all perceptions are true, arguing that what it means is that every instance of sensory presentation (widely construed, to include dreams, hallucinations, and imagination as well as perception proper) consists in the stimulation of a sense-organ by a real object, which is represented in that perception exactly as it is in reality. That thesis presupposes the truth of the physical theory as a whole. It is itself supported by the epistemological principle that it is possible to distinguish truth from falsity only if all perceptions are true. But since the latter thesis is unfalsifiable, it is empty, and cannot therefore refute scepticism.

It seems clear to me that Epicurus considered visions and hallucinations (and therefore the existence of the gods as the sources of those visions) to be true. His notion that the sun is as large as it seems should also be understood in the context of his epistemology.

Here are some excerpts from C. C. W. Taylor

Epicurus is reported by Diogenes Laertius (X. 31) as having said that perceptions (or perhaps ‘the senses’ or ‘sense-impressions’, which are also possible meanings of Epicurus’s own term aistheseis) are among the criteria of truth; this report is confirmed by two passages of Epicurus himself, at DL
X. 50–2 and 147.

By itself this need imply nothing more than the merest common sense; of course perception and the senses must have some role in determining what is the case and what is not, and hence which statements are true and which are false. But the matter is not so straightforward. For, firstly, aisthesis and related words are used in a wider range of contexts than ‘perceptions’ and its cognates: e.g. cases of hallucination are sometimes said to involve aisthesis (see below). Secondly, Epicurus is also said to have maintained the much more obviously controversial thesis that every aisthesis is true. In this paper I shall try to establish what he meant by those statements, to clarify the relation between them, and to consider their
wider implications for his epistemological and physical theory.

I turn first to the doctrine that all aistheseis are true, for which the evidence has been helpfully collected by Gisela Striker. No version of it occurs in the texts of Epicurus himself, but the following doctrines, or versions of the same doctrine, are attributed to him by other writers.

1. Every aistheton is true (Sext. M VIII. 9: Ep. ta men aistheta panta elegen alethe kai onta ... panton de ton aistheton alethon onton; 63: Ep. elege men panta ta aistheta einai alethe, kai pasan phantasian apo hyparchontos einai ...). Cf. M VIII. 355, every aistheton is reliable (bebaion).

2. Every aisthesis and every phantasia is true (Usener, no. 248: Aetius IV.
9. 5; Usener, p. 349, 5–6: Aristocles apud Eus. PE XIV. 20. 9).

3. Every phantasia occurring by means of aisthesis is true (Plut. Col. 1109
a–b).

4. Every phantasia is true (M VII. 203–4, 210).

5. Aisthesis always tells the truth (M VIII. 9: ten te aisthesin ... dia pantos te
aletheuein ; 185: medepote pseudomenes tes aistheseos). Cf. the passages in Cicero referred to by Striker, to the effect that the senses are always truthful.

It appears likely that most of these formulations differ from one another
only verbally. Thus Sextus is the only writer cited above to use the term aistheton (‘sense-content’), and his use of the term strongly suggests that it is interchangeable with phantasia (‘appearance’).

This appears particularly from M VII. 203–4, where the thesis that phantasia is always true is supported by a number of examples from the various senses, e.g. ‘The visible (horaton) not only appears (phainetai) visible, but in addition is of the same kind as it appears to be’, which are summed up in the words ‘So all phantasiai are true.’ Here, then, what is true of aistheta is taken to be true of phantasiai as a whole; further evidence that Sextus regards the terms as coextensive is given by M VIII. 63–4, where he represents Epicurus as counting Orestes’ hallucination of the Furies as a case of aisthesis, and therefore as true.

Again, in the passage from Aristocles cited above, quoted by Eusebius, aisthesis is treated as interchangeable with phantasia, since the thesis introduced by means of both terms (i.e. 2 above), is expressed in the course of the passage firstly as the thesis that every aisthesis is true and then as the thesis that every phantasia is true.

If these writers treat aistheton and phantasia as strictly coextensive terms, they misrepresent Epicurus, who distinguishes phantasiai of the mind (e.g. appearances in dreams) from phantasiai of the senses (DL X. 50–1). In strict Epicurean doctrine, then, aistheta are a species of phantasiai.

But the misrepresentation is not crucial, since Epicurus clearly holds that both sensory and non-sensory phantasiai are always true (ibid.: for the Epicurean view of the ‘truth’ of dreams, see below). In the passages from Sextus cited under above, where aisthesis is said always to tell the truth and never to lie, it is possible to render the word as ‘sense’ (equivalent to ‘the senses’), ‘perception’, ‘sensation’ (i.e. the
faculties thereof), ‘the (particular act of ) perception’, or ‘the (particular)
sensation (occurring in the perceptual context)’.

But however we render it, the thesis that aisthesis always tells the truth is presented either as following immediately from the central thesis that all aistheta are true, or as entailing it, or as restating it. The precise logical relation of the two theses (if indeed they are two) is impossible to determine from these passages; by the same token, their intimate logical interconnection is displayed by both. Our evidence, then, indicates that ancient writers regularly attribute to Epicurus or the Epicureans the doctrines that every phantasia is true and that every aistheton is true. Though strictly aistheta are a species of phantasiai, differentiated by their causation via the sense-organs, some later sources appear to make no distinction between the terms. In some reports the doctrine that every aistheton is true appears to be expressed as ‘Every aisthesis is true’; in others, where aisthesis may mean ‘sense’ or ‘faculty’, the thesis that aisthesis always tells the truth is inextricably interwoven with the thesis
that all aistheta are true.

In the concluding paragraphs he writes

... Epicurus had, then, some good arguments, or at least the materials
of such arguments, which he could advance against scepticism without
presupposing his physical theory. His method thus displays a subtle interaction of epistemological and metaphysical considerations.

The fundamental epistemological requirement is that every aisthesis should be true, i.e. that whatever seems to be the case should in some sense or other actually be the case. It then becomes part of the task of the general theory of nature to specify the sense or senses in which what seems to be actually is. It is an astonishing achievement of atomism, both in its fifth-century and in its Epicurean version, to have provided an even reasonably plausible account
of the satisfaction of this requirement as part of a comprehensive account of the world.

But problems remain. For the sceptic can reasonably claim that the account of how things always are as they seem is, in the last resort, empty. For example, how is the claim that sweetness is always the taste of a
structure of smooth atoms to be tested? Suppose microscopic examination revealed that in some cases the atoms were smooth, but in others spiky.

If both the microscopic and the gustatory observations are, in the theoretical sense, ‘true’, then we have two sets of atoms instead of one. No doubt we could add to the theory a description of how a structure of smooth atoms emits a structure of spiky ones, but the problem of verification arises there again, and so on at every level. The basic difficulty is that a theory of objective reality which is not subject to any constraint by experience must be empty of actual content.

Epicurus could have avoided this difficulty only by abandoning his fundamental epistemological requirement and facing up to the sceptical challenge to find a way of discriminating veridical from non-veridical experience. The subsequent history of philosophy to the present indicates the formidable nature of that undertaking; the Epicurean alternative, though ultimately unsuccessful, was well worth exploring.