Hawthorne explores the theme of aging in his short story "Dr. Heidegger’s Experiment." His story explores questions such as what it means to be old and what it means to be young. The characters in the story reflect these ideas, including the difference between aging physically and aging mentally or emotionally. From the characters (except for Dr. Heidegger himself), it is obvious that age does not necessarily equal wisdom. The theme of aging is depicted in the contrasting characters of the wise doctor and his four subjects. The doctor, who learns from the perplexing and conceited actions the other characters exhibit after drinking the powerful elixir, does not drink the water from the Fountain of Youth:
"For my own part, having had much trouble in growing old, I am in no hurry to grow young again."
His four subjects, on the other hand, rush to drink it and become young again.
"Give us more of this wondrous water!" cried they, eagerly. "We are younger—but we are still too old! Quick—give us more!"
As this quote shows, the elixir brings out the worst in the characters—their thirst for youth can never be satisfied. These details also highlight the fickleness of human desire and happiness that some people expose, an important flaw that Hawthorne exposes with his characters. Whether old or young, the elixir shows that the four characters most certainly can never be happy nor truly know what they need or want.
Another theme of the story is foolishness and arrogance. Even though the four subjects are given another chance at being young again in the same lifetime, they pay no heed when asked if they’ll tread cautiously and avoid the mistakes they made in their 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.
The four guests are blinded by the wondrous gift that the powerful water has given them, and instead, the gift turns into a cruel curse, as the last line shows.
But the doctor's four friends had taught no such lesson to themselves. They resolved forthwith to make a pilgrimage to Florida, and quaff at morning, noon, and night, from the Fountain of Youth.
In this way, Hawthorne intertwines these two prominent themes.