premise

a statement that is assumed to be true and from which a conclusion can be drawn; "on the assumption that he has been injured we can infer that he will not to play"

set forth beforehand, often as an explanation; "He premised these remarks so that his readers might understand"

furnish with a preface or introduction; "She always precedes her lectures with a joke"; "He prefaced his lecture with a critical remark about the institution"

take something as preexisting and given