Will Storm wrote:
Get we go further back. Beyond the establishment of the institution...
why is homosexuality wrong outside of the institution.
The repeated reason that I am still having trouble with is that it somehow diminishes our ability to reason. I know that I am being... slow on this issue but I want to understand the whole thing so that I can defend the Church's decision.
Homosexual marriage is wrong on two levels. First it's not a marriage. Second it's not a sexual act. The reason why it's not a marriage is already discussed above. The reason why it's not a sexual act is because it's contrary to the purpose (recall Aristotle's fourth cause, the final cause) of a sexual act. The main purpose of sexual act of the genitals is to produce offspring. Homosexuality use the sexual organs contrary to its purpose. An infertile heterosexual couple does not use their sexual organs contrary to its purpose because they remain open to the possibility of procreation.
So sexual organ are meant for [ie. it's final cause/purpose is] heterosexual sex, just like how the heart is meant for pumping blood, just like how the kidney is for cleansing blood. We know this. But if after knowing it we use our sexual organ for homosexual act, our heart for cleansing blood and our kidney for pumping blood then we are acting contrary to what we know is the organs purpose [.ie. final cause]. It's like knowing that 1+2=3 but deliberately say that it's 4. Such acts destroy reason. We are being unreasonable.