A prenup doesn't protect you from that possibility. It isn't like insurance. It doesn't provide you with additional funds to deal with an unexpected problem. A prenup is a pre-determined agreement of what you're going to run off with when your relationship fails. It depends on you foreseeing what will be important to you when that happens. And be honest - can you really do that without at least some knowledge of the future?
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I can honestly say that I don't see any reasonable future scenario where we split up and my wife actively seeks to hurt me. I believe that we would amicably part. This can certainly be done without a prenup.
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Maybe I've been soured on prenups from discussions with folks of the men's rights persuasion who are 100% always vocally for them all the time (because women are money grubbin' whores who are always going to screw you donchaknow). I guess that the request can come from a good place.
At their best prenuptials between two people who trust and love each other, both want prenups, both fully understand and agree to the contracts, where no power imbalance in the relationship is enforced, and where the prenuptials are regularly updated as circumstances change over the course of the relationship . . . they have the potential to do less harm than good. Is this the way they're usually done though? It doesn't seem that way from my limited world view.
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The omniscience kinda has to work from the start with a prenup too though. Otherwise you won't be able to plan for and account for the many ways that your partner could screw you. You're still depending on your current trust of the person. Doesn't seem better - maybe just different?
Well, a prenup doesn't provide additional money, or guarantee your partner won't turn into a dick. But it does smooth the path to a divorce in that scenario by establishing a baseline right to XYZ. I've known two situations over the past, say, 25 years where the husband turned out to be a controlling asshole who decided to try to bankrupt the wife as a way to force her to accept a poor settlement (in both cases draining the joint accounts on the way out the door). They both spent a shit-ton of money on lawyers, going before the judge over every single little thing. I think if they had things laid out like "I brought $XX into this marriage and I get it back if the marriage dissolves," that would very much have simplified things before the judge -- at least enough to manage an initial distribution of assets.
(Also I can also guarantee that neither woman thought her husband would turn out to be a controlling asshole in a divorce. Turns out the hidden personality traits that led to the demand for a divorce after 20+ years of marriage also led to a massively unpleasant divorce process. Go figure.)
I can totally agree that many prenups can be used to reinforce a power imbalance, and that that is damaging. But we were talking more generally -- and more specifically here, the OP as the lower-earner was considering asking for a prenup even though that might not actually benefit him.
tl;dr: they're not a panacea, and they can be used for evil, but they also can be useful, even for people who trust their partners. So please don't say that asking for a prenup means you don't trust your partner enough to get married.
Oh, also: many business contracts are written down not because of a lack of trust, but for clarity. I trusted my current contractor enough to give him a $1M contract to rebuild my house post-fire without even getting competitive bids, because I've worked with him twice before and know how he operates. But you'd better believe that contract still specified exactly what we were getting for each line item, so there'd be no confusion and disappointment down the road if it turns out we both assumed different things.