To be necessary, fit, becoming, or expedient; to behoove; -- in this sense formerly sometimes used impersonally or without a subject expressed. Chaucer.
" Ought is now chiefly employed as an auxiliary verb, expressing fitness, expediency, propriety, moral obligation, or the like, in the action or state indicated by the principal verb."
"To speak of this as it ought, would ask a volume."
"Ought not Christ to have suffered these things?"