"For my own part, having had much trouble in growing old, I am in no hurry to grow young again." (17)
Heidegger, like his guests, has suffered in his youth – remember the death of his fiancée. Unlike the four guests, however, Heidegger knows that to become young again would be to make the same mistakes a second time. He has no desire to do this.
"Before you drink, my respectable old friends,'' said he, "it would be well that, with the experience of a lifetime to direct you, you should draw up a few general rules for your guidance, in passing a second time through the perils of youth. Think what a sin and shame it would be, if, with your peculiar advantages, you should not become patterns of virtue and wisdom to all the young people of the age!'' (19)
This is our second tip-off as to the real nature of Dr. Heidegger's experiment, and his real motives in conducting it. The Doctor is concerned with the folly and behavior of youth, not in the medicinal properties of the water from the fountain of youth.
The doctor's four venerable friends made him no answer, except by a feeble and tremulous laugh; so very ridiculous was the idea that, knowing how closely repentance treads behind the steps of error, they should ever go astray again. (20)
This is the second time the narrator has used the word "venerable" to describe Heidegger's four guests (the first time is in the story's opening line). We have to think that the narrator is using the word ironically – especially given that he earlier referred to the four guests as "foul."
There, in fact, stood the four glasses, brimful of this wonderful water, the delicate spray of which, as it effervesced from the surface, resembled the tremulous glitter of diamonds. It was now so nearly sunset that the chamber had grown duskier than ever; but a mild and moonlike splendor gleamed from within the vase, and rested alike on the four guests and on the doctor's venerable figure. (32)
OK, this is the last time we're going to talk about the word "venerable," we promise. But this is the third time Hawthorne has used the word in this very short story, so we ought to pay attention. The first two, we've argued, were ironic – clearly, the foolish old guests are anything but venerable. But what of this usage – now the word is being used to describe Dr. Heidegger! Is it similarly ironic, or does the narrator genuinely believe that the Doctor is worthy of respect?
As they struggled to and fro, the table was over-turned, and the vase dashed into a thousand fragments. The precious Water of Youth flowed in a bright stream across the floor […]
"Come, come, gentlemen! – come, Madam Wycherly,'' exclaimed the doctor, "I really must protest against this riot.'' (42-43)
Dr. Heidegger isn't even upset about the spilled potion! This could either be because he knows it isn't real, or because he's already concluded that he wants nothing to do with growing young again.
"Yes, friends, ye are old again,'' said Dr. Heidegger, "and lo! the Water of Youth is all lavished on the ground. Well – I bemoan it not; for if the fountain gushed at my very doorstep, I would not stoop to bathe my lips in it – no, though its delirium were for years instead of moments. Such is the lesson ye have taught me!'' (51)
Why does Dr. Heidegger assume that, because his guests became fools again when they were young, he himself would do the same thing?
The precious Water of Youth flowed in a bright stream across the floor, moistening the wings of a butterfly, which, grown old in the decline of summer, had alighted there to die. The insect fluttered lightly through the chamber, and settled on the snowy head of Dr. Heidegger. (42)
Only now, at the end of the story, do we hear of Dr. Heidegger's physical appearance – his "snowy head" and, shortly after this passage, "withered lips." For Heidegger, being old is about his venerability and his wisdom, not his aging body. The four guests, however, understand age in a physical way, and so the descriptions we get of them are focused on their bodies.
In truth they had. The Water of Youth possessed merely a virtue more transient than that of wine. The delirium which it created had effervesced away. Yes! they were old again. (50)
The transience of the elixir's effect may be a comment on the transience of youth.