Also, I had a "DUH" moment this morning about something that needs to be included in this thread.
Torquatus does not gve us *only* the "use your eyes and look at the young of all species before they are corrupted" argument.
He also gives us:
(2) A thought experiment (or perhaps an appeal to anticipations, or "conceivability"?) that is probably analogous to the use of the Javelin argument as to the size of the universe:
QuoteXII. The truth of the position that pleasure is the ultimate good will most readily appear from the following illustration. Let us imagine a man living in the continuous enjoyment of numerous and vivid pleasures alike of body and of mind, undisturbed either by the presence or by the prospect of pain: what possible state of existence could we describe as being more excellent or more desirable? One so situated must possess in the first place a strength of mind that is proof against all fear of death or of pain; he will know that death means complete unconsciousness, and that pain is generally light if long and short if strong, so that its intensity is compensated by brief duration and its continuance by diminishing severity. Let such a man moreover have no dread of any supernatural power; let him never suffer the pleasures of the past to fade away, but constantly renew their enjoyment in recollection, and his lot will be one which will not admit of further improvement.
Suppose on the other hand a person crushed beneath the heaviest load of mental and of bodily anguish to which humanity is liable. Grant him no hope of ultimate relief in view also give him no pleasure either present or in prospect. Can one describe or imagine a more pitiable state? If then a life full of pain is the thing most to be avoided, it follows that to live in pain is the highest evil; and this position implies that a life of pleasure is the ultimate good. In fact the mind possesses nothing in itself upon which it can rest as final. Every fear, every sorrow can be traced back to pain; there is no other thing besides pain which is of its own nature capable of causing either anxiety or distress. Pleasure and pain moreover supply the motives of desire and of avoidance, and the springs of conduct generally. This being so, it clearly follows that actions are right and praiseworthy only as being a means to the attainment of a life of pleasure. But that which is not itself a means to anything else, but to which all else is a means, is what the Greeks term the Telos, the highest, ultimate or final Good. It must therefore be admitted that the Chief Good is to live agreeably.
And (3) - a more practical "Why do we do anything that we do?" argument:
QuoteXIII. Those who place the Chief Good in virtue alone are beguiled by the glamour of a name, and do not understand the true demands of nature. If they will consent to listen to Epicurus, they will be delivered from the grossest error. Your school dilates on the transcendent beauty of the virtues; but were they not productive of pleasure, who would deem them either praiseworthy or desirable? We esteem the art of medicine not for its interest as a science, but for its conduciveness to health; the art of navigation is commended for its practical and not its scientific value, because it conveys the rules for sailing a ship with success. So also Wisdom, which must be considered as the art of living, if it effected no result would not be desired; but as it is, it is desired, because it is the artificer that procures and produces pleasure.
I therefore wonder to what extent Torquatus is indeed giving us an example of each of the perspectives he mentions in the opening. And I also wonder to what extent Torquatus represents the "After 300 years of combatting Stoicism we've learned that you better understand the logic side of the argument or you'll get steamrolled" segment of the school, vs the extent to which Lucretius represents the more traditional "here's what you need to know and to hell with the other schools for now" perspective.
If that explains the difference between the two manners of presentation, there is no good reason to "fault" either one, and we need to be fluent in both so that they are both available to use for talking to different people in different circumstances.
And from that perspective Torquatus is not to be criticized entirely for playing the other side's game, but he's dealing with the reality that some people have been "corrupted" by opposing philosophies more than others, and they have to be walked back as it were from the precipice in steps. Others, on the other hand, who are not so far down the road of corruption through skepticism or idealism or supernatural religion can be approach more directly with the "this is the way things work" approach.