Sextus Empiricus Pyrrhoniae Hypotyposes 1.14.128

[128] Nor yet does the mind apprehend it, since, in the first place, its guides, which are the senses, go wrong; and probably, too, the mind itself adds a certain admixture of its own to the messages conveyed by the senses; for we observe that there are certain humours present in each of the regions which the Dogmatists regard as the seat of the ‟Ruling Principle” ¹ — whether it be the brain or the heart, or in whatever part of the creature one chooses to locate it. Thus, according to this Mode also we see that, owing to our inability to make any statement about the real nature of external objects, we are compelled to suspend judgement.