Then the statement of absolute trust is accounted for by the significant rate of mistakes people make.
Alternatively, you can make that statement as part of a strategy to maximize your expected return on a marriage—if the increase in marriage quality from placing absolute trust in your spouse is greater than the expected cost of being disadvantaged in the divorce negotiaions (if your spouse turns out to be untrustworthy), then you might rationally do it anyways.
Then the statement of absolute trust is accounted for by the significant rate of mistakes people make.
Alternatively, you can make that statement as part of a strategy to maximize your expected return on a marriage—if the increase in marriage quality from placing absolute trust in your spouse is greater than the expected cost of being disadvantaged in the divorce negotiaions (if your spouse turns out to be untrustworthy), then you might rationally do it anyways.