Mr. Holgrave is a daguerreotypist, which means that he takes photographs. (Daguerreotypes were an early form of photograph mainly used for portraits.) It makes sense that Mr. Holgrave would have a liking for this particularly kind of photography. After all, he really enjoys observing people. One of the first things Phoebe notices about him is that he is a "calm and cool [...] observer" (12.8). Mr. Holgrave doesn't show his feelings particularly easily, but his sharp eye takes in everything around him.
Mr. Holgrave rents a room from Hepzibah and looks after her garden. He's the one who encourages her to open her little shop at the side of the House of the Seven Gables. He is also a social reformer and is friends with "reformers, temperance lecturers, and all manner of cross-looking philanthropists" (5.58). One of the few times Phoebe actually sees Mr. Holgrave get excited is when he expresses himself on the subject of family inheritances.
Mr. Holgrave thinks families should only get to hold onto their property for 50 years before having to start again. Otherwise the burden of heavy legacies from jerks like Colonel Pyncheon become too heavy. Mr. Holgrave's belief that we should all be nomads seems to come from his personal life experience: he has been supporting himself with multiple jobs for years and he's only 22. He's never settled down, so no wonder he doesn't see the importance of doing so. At least, not until he's actually won Phoebe's heart and begins thinking about starting a family of his own. Then he dreams of houses of stone to leave his kids. Apparently, owning stuff is a fact of life for people, no matter what their youthful politics.
Mr. Holgrave's bright, observant eye lends itself to more than social reform and daguerreotypes. He is also a practicing hypnotist and gives public lectures on the subject. When he reads the legend of Alice Pyncheon to Phoebe, she becomes hypnotized by his gestures. The narrator comments:
To a disposition like Holgrave's, at once speculative and active, there is no temptation so great as the opportunity of acquiring empire over the human spirit; nor any idea more seductive to a young man than to become the arbiter of a girl's destiny. (14.2)
In other words, Mr. Holgrave has a philosophical mind and he's interested in people, so how could he not jump at the chance to control another person, especially a young female person? But because Mr. Holgrave is not a creep (unlike his ancestor, Matthew Maule II), he doesn't take advantage of Phoebe. He wakes her up and tells her that she's been asleep. He respects her enough not to give in to his natural temptation to dominate. (For more on Mr. Holgrave's relationship with Phoebe, check out our thoughts on her character.)
Mr. Holgrave makes a choice that works against his personal inclinations – he chooses right even though he doesn't feel like doing so. The reason we're underlining this is not just because it's a good thing; it's also an interesting counterexample to Judge Pyncheon, who everyone thinks is so doomed to be a bad guy. Even if Judge Pyncheon's nature isn't good, he could have chosen differently. Unlike Mr. Holgrave, he gives in to his bad tendencies.
One last thing about Mr. Holgrave: he is at least partly Hawthorne's own stand-in in the novel. Let's think about how they overlap: Mr. Holgrave has a strong interest in individual psychology, which Hawthorne (as a writer) shares. Mr. Holgrave is an artist who is interested in presenting "the secret character with [...] truth" (6.16). This desire to show the "secret character" of the world's truths sounds a lot like Hawthorne's own "Preface" to The House of the Seven Gables, in pursuit of a "high truth" (source). Both the narrator and Mr. Holgrave use the same phrase – like a "human countenance" (2.1, 13.12) – to describe the effect of the House of the Seven Gables. And they both share names that start with the letter "H." We think that last piece of evidence is particularly persuasive.