He wrote home about this time:—
I go every Sabbath about eleven miles, take charge of a Sabbath school at ten, preach at eleven, have an intermission of half an hour at half past 12, preach again a long sermon, take tea at once, and ride over the chill, bleak prairie, directly home, which I do not reach till late in the evening. On week days, besides the hours of teaching, I lecture and aid in debating-societies, and so forth, so that I can scarcely find time to write even these poor letters.Two years he spent in labors such as these, and then returned to spend two years of study at the Divinity School of Harvard University. To revert to the pursuits of the student was, however, rather hard for one who had already lived the stirring life of a pioneer preacher; and his zeal was constantly bursting over the cautious regulations of the Faculty,—he naturally demeaning himself as a full-fledged minister instead of a pupil. Much of his time was given, therefore, to extraneous occupation, though he graduated with his class in 1847. This partial separation of pursuits, added to some peculiarities of temperament, and a rather marked use of evangelical phrases and methods, formed undoubtedly some slight barrier between Arthur Fuller and many of his companions, both at this time and afterwards. Having been accustomed to express his opinions with the greatest freedom and unction to Western audiences by no means his equals in education, he had not always the necessary tact in dealing with his equals, and hence was apt to elicit as much antagonism as sympathy. If he erred, however, everybody admitted that it was from excess of zeal; but it is difficult to make such zeal attractive, especially among cultivated intellectualists, and certainly he did not always succeed. His intense earnestness had, or seemed to have, a flavor of self-assertion, and this often led his critics to do him less than justice. The recollection of this peculiarity in him, whatever may have been its source, added interest to his later career in the army; for it is evident that the grander experiences of life smoothed away some of these roughnesses, and developed in him more comprehensiveness, more tact, and more power of adaptation.