College education
Weld then (1825) attended classes at Hamilton College in Clinton, Oneida County, New York, though he did not enroll as a student and does not appear in the College's published lists of students. About 1825 he stayed at the College in the suite of tutor William Kirkland, and not only attended classes but was "something of a leader among the students". The famous evangelist Charles Grandison Finney was based in Oneida County, and according to him, Weld "held a very prominent place among the students of Hamilton College, and had a very great influence." He described himself as "educated at Hamilton College." However, Hamilton turned down his proposal of a manual labor program.
While a student Weld attended some of Finney's many revivals, for he became Finney's disciple. In Utica, intellectual capital of western New York, center of abolitionism, and county seat of Oneida County, he met and became a good friend of Charles Stuart, an early abolitionist, who at that time (1822–1829) was head of the Utica Academy. They spent several years as members of Finney's "holy band".
In the winter of 1827, he and his brother Charles worked on a whaling vessel in Labrador.
Later in 1827, abandoning Hamilton on Stuart's recommendation, he enrolled in the new Oneida Institute of Science and Industry in nearby Whitesboro, New York, the most abolitionist school in the country, his fees paid for him by Stuart, after first participating in a pilot program, staying at the farmhouse of founder George Washington Gale in Western, New York, working in exchange for instruction. While at the Oneida Institute, where he was in charge of the cow-milking operation, he would spend two weeks at a time traveling about, lecturing on the virtues of manual labor, temperance, and moral reform. "Weld...had both the stamina and charisma to hold listeners spellbound for three hours." As a result, by 1831 he had become a "well known citizen" of Oneida County, according to a letter of Joseph Swan published in the Utica Elucidator.
Weld was described thus by James Fairchild, who knew him from when they were students together at Oberlin (of which Fairchild would later be President):
Among these students was Theodore D. Weld, a young man of surpassing eloquence and logical powers, and of a personal influence even more fascinating than his eloquence. I state the impression which I had of him as a boy, and it may seem extravagant, but I have seen crowds of bearded men held spell-bound by his power for hours together, and for twenty evenings in succession.
In an editorial comment in The Liberator, presumably by its editor Garrison, "Weld is destined to be one of the great men not of America merely, but of the world. His mind is full of strength, proportion, beauty, and majesty. ...[In his writing] there is indubitable evidence of intellectual grandeur and moral power."
In his reminiscences of that period Dr. Beecher observed:
Weld was a genius. ...In the estimation of the class, he was president. He took the lead of the whole institution. The young men had, many of them, been under his care, and they thought he was a god. We never quarreled, however.
In a completely different forum, William Garrison said that in a convention of antislavery "agents", who travelled from town to town giving abolitionist lectures and setting up new local anti-slavery societies, "Weld was the central luminary around which they all revolved".
His future wife Angelina Grimké said in 1836, when she first laid eyes on him and heard him speak for two hours on "What is slavery?", that "I never heard so grand & beautiful an exposition of the dignity & nobility of man in my life".