Partners opinions

Do you think that the way your SO thinks in a relationship goes a long way and leads to the type of person they are & how’d they react being in that situation. For example lets say you & your partner are tlking about cheating and their like well it happens or you guys are talking about marriage and they say marriage is about forgiving even through the really bad (cheating, hurtful situations etc) or if they don’t even believe in marriage meaning they won’t ever even marry you. Do you think ur SO’s opinions on certain topics contributes to them as a person and how they’d personally react being put in that situation is really my question ? Another example .. if they try to justify cheating or abuse etc. just an example