One explanation of the sabbath
Measuring social idleness
Given that the primary purpose of human society is to increase the idleness of its members, it is also necessary for a society to measure its idleness, in order to see whether social idleness is increasing or decreasing.
In ordinary circumstances, one may suppose that each person carries out his required duties as and when they become necessary. Work is intermittent. And in this circumstance, it is impossible to simply rely upon each member's estimate of his own efforts, because these estimates may be wildly inaccurate, or inflated, or underreported.
An alternative is to take some period of time, seven to ten days, and require that at the outset of this period all members of society should work diligently and continuously to perform all the tasks that are necessary for the maintenance of society for that period of time. And that when they have completed their work, they should do no further work until the outset of the next period. And so rather than have work and play alternate throughout each day, busy and idle times become strictly separated into the working week and the sabbath or weekend.
Here all the food and vegetables required for the period are collected in the first few days of the period. And all the water hauled. And all the firewood gathered. And all the food cooked. And all the clothes and shoes made and repaired. And all the tools made and repaired.
In this way, as people complete their tasks, and are 'signed off' from work by a supervisor whose task is to note when they completed their duties, it becomes possible to assess the idleness of society simply by subtracting the total time worked from the duration of the period. Thus if, on average each person works 4 days in every 10 days to perform their allotted tasks, then the idleness of that society is (10 - 4)/10 or 60%.
There would seem to be a built-in incentive in this system for people to work hard, in that the sooner they complete their work, the sooner they enjoy the leisure and freedom of the sabbath.
And also it is possible to determine who is working longer than others, and who working less. And so, for the purposes of equality, those who end their tasks early may be sent to assist those who have yet to complete their tasks, until all present themselves to be signed off work simultaneously.
And in this way also the effect of employing new tools or techniques may also be measured. Where truly useful tools come into use, the effect will be to increase the idleness of society. If the tools are of less value than their cost, and are luxuries, their use will decrease social idleness.
It is, of course, important that during the period of work that everyone work to the best of their ability. And it is equally important that during the period of idleness that nobody do any work. For to the extent that they do not work assiduously, or perform work during idle time, to that extent the measure of the society's idleness becomes inaccurate.
Of course, it will inevitably happen that some work must periodically be done during the idle sabbath. And during the work week, there must be periodic respites from work.
Thus, in very idle societies, the sabbath would fill most of the week. And in the least idle societies, the sabbath might contract to a half day or less.
Whatever the origins of the sabbath, the current Judaic, Christian, and Muslim one day in seven seems more to be a defensive measure to ensure that, in inegalitarian societies, where some work long hours and others next to none, those who work the longest are ensured at least one day of leisure.