Is it possible to affirm human equality without religion?Sure. Indeed, it is often more difficult within religion. Jews consider themselves "the chosen people," in certain brands of Christianity like Calvinism there is the notion of "the saved," and in others the idea of being "born again" or "forgiven," all of which serve to priviledge those inside the group. One of the ways that religions as organizations increase and maintain their memberships is to offer metaphysical perks which require denying equivalence between those in the club and those outside. Without the artificial lines between groups imposed by religions, one can fall back on a species notion and affirm equality of everyone within the species.
Of course, the question is always, "What sort of equality?" In any multitude of fashions, humans aren't equal and that inequality is confirmed by observation. Some are taller, some are smarter, some are faster, some can roll their tongues, some get more dates,... If we are talking about equal rights under the law, then a social contract will do the trick. If we are talking about equal in terms of moral considerability, then something along the lines of utilitarianism would give you equality of considerability.
Soul Searcher asks,
How is it that I made it through 18 years of schooling (K-12, 4 undergrad, 1 grad school) and I am only now learning the proper usage of which and that when introducing non-restrictive and restrictive clauses?Perhaps it is because Harvard is so restrictive.
The teaching of grammar has become less important as two things have happened: (1) as a society, adherence to grammatical rules has been greatly relaxed -- for example, splitting infinitives is no longer verboten, very educated people will regularly use the word "quote" as a noun, and "they" is widely accepted as a gender neutral singular third person pronoun. We have become much less interested in formalized rules of grammar and more with the style and effectiveness of communication. (2) When we teach nowadays, we are aware that students learn through writing and by hanging them up on grammar, we discourage them from seeing writing as a toolthey feel confident to use. As such, grammar classes have become language arts classes focusing less on grammatical precision than on ideas. This appraoch has been in place long enough that those who are grading the papers were schooled in that fashion and it has become standard that which/that confusion won't even be noted.
Language is a living thing. Grammarians are social scientists not usage cops; they catalogue what is considered a well-formed sentence. Liguistic rules change over time. That's not to say that there are not rules. Of course there are. There need to be in order to avoid ambiguitiy and facilitate clarity in expression. Having a firm grasp on grammar does make one a stronger, clearer, better writer. There are grammatical errors, but there are also situations in which violating the rule does not hamper the understanding of the utterer's meaning. Many which/that mistakes fall in that class.
UPDATE: While we're talking about grammar, check out on of my new favorites, The "Blog" of "Unnecessary" Quotation Marks. The ghost of Chris Farley lives on.