I hate to be the bearer of bad news ... but you can't reject a proposed premise just because you don't like it. You may claim ignorance and give the proposer an opportunity to educate you OR you may give a valid reason for your rejection.
1. You may reject a premise that is easily refuted ... often because it is too sweeping or so vague as to be misleading. An example that is too sweeping (and it apt to catch some readers) is "The Catholic Church does not allow married priests." That is easily refuted on two grounds
- In the Eastern Rite the usual rule is along the lines of a married priest may not become a bishop and an unmarried deacon may not marry
"CAN. 373† Clerical celibacy chosen for the sake of the kingdom of heaven and highly suited to the priesthood is to be greatly esteemed everywhere, according to the tradition of the entire Church; likewise, the state of married clerics, sanctioned in the practice of primitive Church and in the Eastern Churches through the ages, is to be held in honor.
CAN. 374† Clerics, celibate as well as married, should shine forth with the splendor of chastity; it is for particular law to establish suitable means to attain this end.
CAN. 375† Married clerics are to offer an outstanding example to other Christian faithful in conducting family life and in educating children.
john paul, “Apostolic Constitution Sacri Canones,” in Code of Canons of the Eastern Churches: New English Translation (Washington, DC: Canon Law Society of America, 2001), 151–152."
- validly ordained clerics converting to the Catholic Church may be married ... in the US that normally translates to Episcopalian priests.
2. The premise is a Priori false e.g. he did not feel his itch. An itch by definition is felt by the person with the itch. Now if he was walking through poison ivy, another person may assume someone ought to itch ... but not that they do itch.
3. The premise offered is inconsistent with another premise e.g. John is a bachelor; The name of John's wife is Natalie. ... um, bachelors are unmarried - they don't have wives. Unfortunately, the inconsistency of premises given in actual debates are considerably more subtle. Here the opponent must make a choice between their inconsistent premises.
4. The premise contains vague terms/ambiguous terms that must be defined (if possible) before you accept the premise. For example, the lake is too cold and deep for youth to swim in. How cold is too cold? How deep is too deep? What is the age range for "youth"? In religious discussions this often takes the form of definitions not being the same. In a recent discussion on whether or not baptism is a requirement for salvation, my definition of baptism included "baptism of desire" ... a concept completely foreign to my opponent. So always error on the side of assuming a term is vague unless you KNOW that you agree on the meaning of the words.
5. The final reason for rejecting a premise is that it "begs the question" as defined by wikipedia:
To beg a question means to assume the conclusion of an argument—a type of circular reasoning. This is an informal fallacy, in which an arguer includes the conclusion to be proven within a premise of the argument, often in an indirect way such that its presence within the premise is hidden or at least not easily apparent.
The term "begging the question", as this is usually phrased, originated in the 16th century as a mistranslation of the Latin petitio principii, which actually translates as "assuming the initial point". In modern vernacular usage, "to beg the question" is sometimes used to mean "to invite the question" (as in "This begs the question of whether...") or "to dodge a question"
Unfortunately, this is so common a fallacy in religious discussions that I don't dare give an example.
