Our Gemara on Amud Aleph discusses the opinion of Rabbi Nassan who holds that if two people or agents caused damage, though they split the payment, if one is unable to pay, the other assumes 100% liability. Rabbi Nassan seems to hold that instead of looking at each damager to be 50% responsible, we look at each one as 100% responsible. It just so happens that ordinarily since both can pay the debt, they split the cost. But when one cannot pay, the other must make full restitution.

This idea of whether a shared responsibility is considered as fractionally divided amongst the parties or whether all parties are fully responsible can be applied in the social contract as well. When two people are responsible for something, do each of them see themselves as fully responsible, even when the other does their share?

In relationships, it is key to avoid a pattern of measuring or comparing output. Often, counting how much you do versus how much the other does leads to frustration and making you feel even more resentful. There may be cognitive biases that emphasize and cause you to notice how hard you are working, versus your spouse. A better model for behavior in a relationship is values based, and not reactive. The person’s behavior should not be contingent on the other spouse’s actions, but based on what is believed to be a good spouse. Couples can discuss definitions of responsibilities and agree upon roles, but the day-to-day actions or inactions cannot be retaliation.

Often when a relationship heads into a downward spiral, each will feel the other somehow “started”, and they are only reacting. While this might be technically true, it also could be that the other may have unwittingly caused hurt or distance first. That is why it is wise to behave based on what you believe a spouse should do, not based on how your spouse treated you today. I emphasize that this doesn’t preclude discussing overall trends, and to confront patterns of failure to live up to expectations - just don’t make your actions contingent upon it.

If our behavior is reactive instead of values-based we will end up getting lost in cycles of tit for tat. It also is a violation of the halakhic definition of nekama, which is defined as withholding a chesed from another based on how you were previously treated.  (“Do not take revenge nor bear a grudge.” Vayikra 19:18. The Gemara (Yoma 23a) defines what exactly constitutes taking revenge:  Taking revenge is when one asks his neighbor to lend him his saw and he says 'No.'  The next day, his neighbor asks to borrow his axe and he says, 'I will not lend it to you just as you did not lend to me.)

It is statistically likely that spouses will have strengths and weaknesses in different areas, and it also is likely in many areas one spouse could carry more of the load. This alone is not a problem. In almost any system, micro or macro, such as families or government, it is given that some individuals will far exceed others in contribution and productivity. Such inequities are stable, so long as there is a general sense that each person is doing the best they can. By each person taking 100% responsibility for the relationship stability, there is a good chance that between the human imperfections of each person, the other can compensate and cover. Even when gaps or unfairness becomes apparent, the problem stays localized and isn’t translated into a cycle of withdrawal or retaliation. The issue is confronted, but if one doesn’t do their 50% share, the other still meanwhile takes full responsibility. 

I say meanwhile, because every situation has limits. If a person is in a relationship where there is consistent lack of responsibility taking, and extended periods of not putting in reasonable efforts, sometimes it’s only fair that the functioning spouse be allowed to leave the relationship and find a suitable partner in life if there is no effort nor hope for progress. Even so, a decision to divorce based on a spouse’s failure to meet minimum standards of a relationship does not justify withholding or retaliation while still in the relationship. Divorce may be halakhically permitted, but revenge is not.