They reject dialectic as superfluous; holding that in their inquiries the physicists should be content to employ the ordinary terms for things.An opinion often emphasized: e.g.§§ 37, 73, 82, 152. Cf. Lucr. iii. 931 sqq.Now in Epicurus affirms that our sensations and preconceptions and our feelings are the standards of truth; the Epicureans generally make perceptions of mental presentationsSuch mental pictures are caused by atoms too fine to affect sense: cf.§ 64infra; Lucr. ii. 740 sqq., iv. 722 sqq.; Cic. i. 54. On the whole subject consult Usener’s , Fr. 242-265, and, more especially, Sext. Emp. vii. 203-216. to be also standards. His own statements are also to be found in the addressed to Herodotus and in the Every sensation, he says, is devoid of reason and incapable of memory; for neither is it self-caused nor, regarded as having an external cause, can it add anything thereto or take anything therefrom. Nor is there anything which can refute sensations or convict them of error:

one sensation cannot convict another and kindred sensation, for they are equally valid; nor can one sensation refute another which is not kindred but heterogeneous, for the objects which the two senses judge are not the sameCf. inf.§ 146.; nor again can reason refute them, for reason is wholly dependent on sensation; nor can one sense refute another, since we pay equal heed to all. And the reality of separate perceptions guaranteesi.e. the trustworthiness of the senses (αἰσθής εων) considered as faculties of sense-perception: cf. Sext. Emp. viii. 9 (Usener, Fr. 244). the truth of our senses. But seeing and hearing are just as real as feeling pain. Hence it is from plain facts that we must start when we draw inferences about the unknown.More precisely ἄδηλον = that which does not come within the range of sense. Compare e.g.§ 38 τὸ προσμέν ον καὶ τὸ ἄδηλον, and the way in which the conception of void is obtained in § 40. In § 62 it is called τὸ προσδοξαζόμενον περὶ τοῦ ἀοράτου. For all our notions are derived from perceptions, either by actual contact or by analogy, or resemblance, or composition, with some slight aid from reasoning. And the objects presented to madmenCf. Sext. Emp. viii. 63. and to people in dreams are true, for they produce effects—i.e. movements in the mind—which that which is unreal never does.