This post starts with two versions of the key material from Lucretius, then includes other references of significance to this topic:
1743 Daniel Browne Edition - Book Five:
Nature compelled them to use the various sounds of the tongue, and convenience taught them to express the names of things; like children, before they can well speak, are forced to make use of signs, and are obliged to point with their fingers to the objects that lie before them; for every creature is sensible what faculties it has, and how it is to use them. So calves, before the horns appear upon their foreheads, will but fiercely, and push with them, when they are enraged, and the welts of panthers and lions will defend themselves with their claws and feet and teeth when their claws and teeth are scared to be seen; and all kinds of birds, we observe, trust to their wings, and rely upon the fluttering support of their pinions.
But to think that one man gave names to all things, and that men from thence learned the first elements of speech, is absurd and ridiculous; for why should one man distinguish everything by a name, and use the various accents of the tongue, and at the same time another not be as capable of doing this as he?
Besides, if others had not the use of words among them as soon, how could they be made acquainted with the use of them? Or by what art would this one man make them know and understand what he designed? One alone could not compel the rest, and by force make them learn the catalog of his names. He could not prevail by reason, or persuade men so unfit to hear, to do as he directed. Nor would they bear with patience, or by any means endure, to have strange sounds of unintelligible words any longer rattling in their ears to no purpose.
And then, what is there so very wonderful in this, that men, to whom Nature has given a voice and a tongue, should, according to the various knowledge they had conceived of the great variety of things, distinguish each of them by a proper name; when mute cattle, and the several kinds of wild beasts, express their passions by different voices and sounds, when their fear, their grief, or their joys are strong upon them? And that they do so you may observe from evident examples.
For when fierce mastiffs are at first provoked, they snarl, and grin, and show their hard white teeth, and threaten, in their rage, with lower sounds than those they rend the air with when they bark and roar aloud; but when they gently lick their whelps with their soft tongue, or toss them with their feet, or seem to bite, and finally gape as if to eat them up, but never touch them with their teeth, they show their pleasure with a whining voice; not so, as when they howl, left by themselves at home, or when they whimper, with their crouching bodies, to shun the coming blow.
And does not the horse with different neighings fill the air, when, hot in blood and in the prime of youth, he is sorely galled with spurs of winged love, and rages in his lust among the mares, and, eager to engage, with open nostrils snuffs the scent? Does not he shake his trembling limbs, and neigh, for other reasons, with far other sounds?
And then, the feathered race, the various kinds of birds, the hawk, the osprey, and the seagulls, that live and seek their food in the salt waves, they throw out other notes at other times, than when they strive for food and fight for prey; and some will change their hoarse voice according to the different qualities of the air, as the long-lived ravens, and the flocks of crows, when they are said to call for rain and showers, and sometimes to cry for wind and storms. If therefore the different perceptions of things will compel these creatures, mute as they are, to send out different sounds, how much more reasonable is it that men should be able to mark out different things by different names?
Cyril Bailey Edition:
Then after they got themselves huts and skins and fire, and woman yoked with man retired to a single [home, and the laws of marriage] were learnt, and they saw children sprung from them, then first the race of man began to soften. For fire brought it about that their chilly limbs could not now so well bear cold under the roof of heaven, and Venus lessened their strength, and children, by their winning ways, easily broke down the haughty will of their parents. Then, too, neighbours began eagerly to form friendship one with another, not to hurt or be harmed, and they commended to mercy children and the race of women, when with cries and gestures they taught by broken words that ’tis right for all men to have pity on the weak. Yet not in all ways could unity be begotten, but a good part, the larger part, would keep their compacts loyally; or else the human race would even then have been all destroyed, nor could breeding have prolonged the generations until now.
But the diverse sounds of the tongue nature constrained men to utter, and use shaped the names of things, in a manner not far other than the very speechlessness of their tongue is seen to lead children on to gesture, when it makes them point out with the finger the things that are before their eyes. For every one feels to what purpose he can use his own powers. Before the horns of a calf appear and sprout from his forehead, he butts with them when angry, and pushes passionately. But the whelps of panthers and lion-cubs already fight with claws and feet and biting, when their teeth and claws are scarce yet formed. Further, we see all the tribe of winged fowls trusting to their wings, and seeking an unsteady aid from their pinions. Again, to think that any one then parcelled out names to things, and that from him men learnt their first words, is mere folly. For why should he be able to mark off all things by words, and to utter the diverse sounds of the tongue, and at the same time others be thought unable to do this? Moreover, if others too had not used words to one another, whence was implanted in him the concept of their use; whence was he given the first power to know and see in his mind what he wanted to do? Likewise one man could not avail to constrain many, and vanquish them to his will, that they should be willing to learn all his names for things; nor indeed is it easy in any way to teach and persuade the deaf what it is needful to do; for they would not endure it, nor in any way suffer the sounds of words unheard before to batter on their ears any more to no purpose.
Lastly, what is there so marvellous in this, if the human race, with strong voice and tongue, should mark off things with diverse sounds for diverse feelings? When the dumb cattle, yea and the races of wild beasts are wont to give forth diverse unlike sounds, when they are in fear or pain, or again when their joys grow strong. Yea verily, this we may learn from things clear to see. When the large loose lips of Molossian dogs start to snarl in anger, baring their hard teeth, thus drawn back in rage, they threaten with a noise far other than when they bark and fill all around with their clamour. Yet when they essay fondly to lick their cubs with their tongue, or when they toss them with their feet, and making for them with open mouth, feign gently to swallow them, checking their closing teeth, they fondle them with growling voice in a way far other than when left alone in the house they bay, or when whining they shrink from a beating with cringing body. Again, is not neighing seen to differ likewise, when a young stallion in the flower of his years rages among the mares, pricked by the spur of winged love, and from spreading nostrils snorts for the fray, and when, it may be, at other times he whinnies with trembling limbs? Lastly, the tribe of winged fowls and the diverse birds, hawks and ospreys and gulls amid the sea-waves, seeking in the salt waters for life and livelihood, utter at other times cries far other than when they are struggling for their food and fighting for their prey. And some of them change their harsh notes with the weather, as the long-lived tribes of crows and flocks of rooks, when they are said to cry for water and rains, and anon to summon the winds and breezes. And so, if diverse feelings constrain animals, though they are dumb, to utter diverse sounds, how much more likely is it that mortals should then have been able to mark off things unlike with one sound and another.
Epicurus from the Letter to Herodotus:
First of all, Herodotus, we must grasp the ideas attached to words, in order that we may be able to refer to them and so to judge the inferences of opinion or problems of investigation or reflection, so that we may not either leave everything uncertain and go on explaining to infinity or use words devoid of meaning.
For this purpose it is essential that the first mental image associated with each word should be regarded, and that there should be no need of explanation, if we are really to have a standard to which to refer a problem of investigation or reflection or a mental inference.
And besides we must keep all our investigations in accord with our sensations, and in particular with the immediate apprehensions whether of the mind or of any one of the instruments of judgment, and likewise in accord with the feelings existing in us, in order that we may have indications whereby we may judge both the problem of sense perception and the unseen.
Having made these points clear, we must now consider things imperceptible to the senses.
Epicurus Principal Doctrines
22. We must consider both the real purpose, and all the evidence of direct perception, to which we always refer the conclusions of opinion; otherwise, all will be full of doubt and confusion.
23. If you fight against all sensations, you will have no standard by which to judge even those of them which you say are false.
24. If you reject any single sensation, and fail to distinguish between the conclusion of opinion, as to the appearance awaiting confirmation, and that which is actually given by the sensation or feeling, or each intuitive apprehension of the mind, you will confound all other sensations, as well, with the same groundless opinion, so that you will reject every standard of judgment. And if among the mental images created by your opinion you affirm both that which awaits confirmation, and that which does not, you will not escape error, since you will have preserved the whole cause of doubt in every judgment between what is right and what is wrong.
25. If on each occasion, instead of referring your actions to the end of nature, you turn to some other, nearer, standard, when you are making a choice or an avoidance, your actions will not be consistent with your principles.
Commentary By Norman DeWitt:
Lucretius Book Four (Daniel Browne Edition):
Many more things of this kind we observe and wonder at, which attempt to overthrow the certainty of our senses, but to no purpose - for things of this sort generally deceive us upon account of the judgment of the mind which we apply to them, and so we conclude we see things which we really do not; for nothing is more difficult than to distinguish things clear and plain from such as are doubtful, to which the mind is ready to add its assent, as it is inclined to believe everything imparted by the senses.
Lastly, if anyone thinks that he knows nothing, he cannot be sure that he knows this, when he confesses that he knows nothing at all. I shall avoid disputing with such a trifler, who perverts all things, and like a tumbler with his head prone to the earth, can go no otherwise than backwards.
And yet allow that he knows this, I would ask (since he had nothing before, to lead him into such a knowledge) from whence he had the notion what it was to know, or not to know; what was it that gave him an idea of Truth or Falsehood, and what taught him to distinguish between doubt and certainty?
You will find that knowledge of truth is originally derived from the senses, nor can the senses be contradicted, for whatever is able by the evidence of an opposite truth to convince the senses of falsehood, must be something of greater certainty than they. But what can deserve greater credit than the senses require from us? Will reason, derived from erring sense, claim the privilege to contradict it? Reason – that depends wholly upon the senses,which unless you allow to be true, all reason must be false. Can the ears correct the eyes? Or the touch the ears? Or will taste confute the touch? Or shall the nose or eyes convince the rest?
This, I think, cannot be, for every sense has a separate faculty of its own, each has its distinct powers; and therefore an object, soft or hard, hot or cold, must necessarily be distinguished as soft or hard, hot or cold, by one sense separately, that is, the touch. It is the sole province of another, the sight, to perceive the colors of things, and the several properties that belong to them. The taste has a distinct office. Odors particularly affect the smell, and sound the ears. And therefore it cannot be that one sense should correct another, nor can the same sense correct itself, since an equal credit ought to be given to each; and therefore whatever the senses at any time discover to us must be certain.
And though reason is not able to assign a cause why an object that is really four-square when near, should appear round when seen at a distance; yet, if we cannot explain this difficulty, it is better to give any solution, even a false one, than to deliver up all Certainty out of our power, to break in upon our first principle of belief, and tear up all foundations upon which our life and security depend. For not only all reason must be overthrown, but life itself must be immediately extinguished, unless you give credit to your senses. These direct you to fly from a precipice and other evils of this sort which are to be avoided, and to pursue what tends to your security. All therefore is nothing more than an empty parade of words that can be offered against the certainty of sense.
Lastly, as in a building, if the principle rule of the artificer be not true, if his line be not exact, or his level bear in to the least to either side, every thing must needs be wrong and crooked, the whole fabric must be ill-shaped, declining, hanging over, leaning and irregular, so that some parts will seem ready to fall and tumble down, because the whole was at first disordered by false principles. So the reason of things must of necessity be wrong and false which is founded upon a false representation of the senses.