Mr Otis is clearly forceful and direct. He openly speaks his mind as illustrated when he speaks to Lord Canterbury about the ghost. He tells the lord that if such a thing existed, it would be used in a roadshow or put on display in a museum. This further indicates that he is not at all superstitious and is a realist, one who deals with things as they are and does not believe in fantasy or any such mumbo-jumbo. He is entirely matter-of-fact with regard to whatever he is told. This aspect is displayed in the manner in which he responds to Mrs Umney's fainting, suggesting that she should be penalized financially for breakages in service if she should repeatedly faint.
Mr Otis comes across as very patriotic. He is also loyal to his party as he is described as a 'true republican.' As a minister, it is obvious that he should display these qualities, but he took it a step further by naming his oldest son Washington. The mocking reference to the twins as 'The Stars and Stripes,' also alludes to the to the American flag.
Mr Otis evidently is a fearless man. This is most pertinently illustrated in his many confrontations with the ghost. In his first encounter with the supernatural entity, for example, he does not panic or become afraid. He, instead, treats the phantom as he would any ordinary person. He, furthermore, dispenses advice and suggests that the spirit oil its chains since they make so much noise. This also shows that he is a practical man who would readily seek solutions to problems.
Another character trait the minister exhibits is the fact that he is prepared to admit that he is wrong and is willing to change his mind. This becomes evident when he changes his opinion about the ghost and accepts its existence. The manner in which he deals with it also emphasizes his practical, hands-on nature - he suggests later, for example, that they would have to remove the ghost's chains from him if he refuses to use the oil he had been offered to lessen the noise they made.
The text also identifies Mr Otis as studious and open-minded. He has been preparing a 'great work' on the history of the Democratic Party, even though he is also called a 'true republican.' It is also apparent that he cares much for his family for, when Virginia disappeared, he did everything he possibly could to find her and, in the process also took care of his wife. The minister is also, obviously, not a materialistic person. When they found precious jewels which the ghost had given Virginia, he insisted that Lord Canterville should take possession of them and was quite distraught when the lord refused. He eventually acceded to Canterville's request that Virginia should be the owner.
Finally, it is evident that the minister is a down-to-earth man. He does not, throughout the story, claim any privileges by virtue of his title and seems to have a reasonably neutral opinion of the gentry. He shows and speaks about them as he would of any other, but does seem to be somewhat dismissive of the pomposity that is a characteristic of this class, as he informs Lord Canterville in their discussion about the jewels:
I feel sure that you will recognize how impossible it would be for me to allow them to remain in the possession of any member of my family; and, indeed, all such vain gauds and toys, however suitable or necessary to the dignity of the British aristocracy, would be completely out of place among those who have been brought up on the severe, and I believe immortal, principles of Republican simplicity.
This is further confirmed in a later statement:
Mr. Otis was extremely fond of the young Duke personally, but, theoretically, he objected to titles, and, to use his own words, "was not without apprehension lest, amid the enervating influences of a pleasure-loving aristocracy, the true principles of Republican simplicity should be forgotten."