近年「同性婚姻」被稱為「婚姻平權」，因為支持者認為同性婚姻是一種平等人權法。本文並不企圖直接論證同性婚姻不是人權，而只是指出很多試圖證明同性婚姻是人權的論據都有不少問題。首先，我會處理一些支持同性婚姻的常見論點，例如「支持同性婚姻＝讓所有人追求幸福」，「反對同性婚姻＝性傾向歧視」，「反對同性婚姻＝神權」，「同性婚姻＝與國際接軌」，「同等對待＝婚姻平權」，「同性婚姻是國際人權的共識」等等。有些人批評筆者過於僵化地理解人權，並傾向假設「人權」愈多愈好，我對這些觀點作出回應。然後我探討同性婚姻與多元婚姻的關係，我列出九種對婚姻的理解 [(M1)－(M9)]，然後大體歸納為四種立場：(P1) 一夫一妻制；(P2) 兩人婚姻制；(P3) 局部婚姻平權；和 (P4) 徹底婚姻平權。我嘗試論證：若支持同性婚姻者 (P2) 不承認其立場是非理性的，又要避免自相矛盾，那他們應提出一些原則性的理據 (X)，而這些原則性的理據在邏輯上一概不會支持 (M3)－(M9)，而只支持(M2)。我認為同性婚姻的支持者還沒有滿意交待 X 可以是甚麼。最後，我批評支持者的另外兩個常用論據：「婚姻沒有本質」，和「同性婚姻是人權，不用訴諸社會共識」。我再解釋婚姻制度是一種鼓勵和嘉獎，而一夫一妻的自然婚姻能清晰解答婚姻權的判準的問題。我的結論是，「同性婚姻是人權」這種說法還待理性論證。

Recently same-sex marriage is often called “marriage equality” because the supporters think that same-sex marriage is a kind of equal human right. In this article, I do not claim to prove directly that same-sex marriage is not a human right, but attempt to point out the problems with many arguments which purport to show that same-sex marriage is a human right. Firstly, I deal with some common arguments used to support same-sex marriage, such as “to support same-sex marriage is to let everyone pursue his happiness,” “objection to samesex marriage is a kind of sexual orientation discrimination,” “objection to samesex marriage is a kind of theocracy,” “accepting same-sex marriage is conforming to the international society,” “marriage equality requires identical treatment,” “same-sex marriage is based on an international consensus on human rights.” Some critics allege that my understanding of human rights is too rigid, and they incline to think the more “human rights,” the better. I respond to these viewpoints. Then I explore the relationship between same-sex marriage & polyamory. I list nine kinds of marriage rights [(M1)－(M9)], and then point out there can be four positions: (P1) monogamy; (P2) two-person marriage; (P3) partial “marriage equality”; and (P4) complete “marriage equality.” I try to argue that if supporters of same-sex marriage do not acknowledge their position is irrational, and also want to avoid self-contradiction, they need to provide a principled ground (X), which only support (M2) without supporting (M3)－(M9). I argue that they have not satisfactorily explained what X can be. Finally, I evaluate two other arguments for same-sex marriage: “marriage has no essence,” and “since samesex marriage is a human right, it does not need the support of a social consensus.” I also explain why the marriage system is a kind of encouragement and reward. Moreover, monogamy can have a clear answer to the question about the criterion of marriage rights. My conclusion is that it remains to be seen what rational arguments can be used to prove that same-sex marriage is a human right.