Given the axiom that social reality consists of individuals and their interactions, and the conjecture that the interesting way individuals interact is through choice, this paper explicates three postulates in four stages:

1) choices are made up of ‘entrained’ sub-choices: thoughts and acts that must be made for the pursuit of another goal;

2) a sub-choice ‘entrained’ in all other choices is a choice for ‘predictability’: a quasi-Bayesian assessment whereby the greater an option’s predictability, the more likely it is to be chosen;

3) it is axiomatic that decisions should always be informed by as many truths and as few falsehoods as possible; true ‘is’ statements can only result in more fulfilling ‘ought’ statements;

4) 1 and 2, and their implications, constitute ‘is’s of sociodynamics, generating a moral and ethical ‘ought’ which I will call ‘Political Existentialism’, a stance that should inform ways in which we organize and run our societies to allow the pursuit of Eudaimonia.

Both concepts point to a sociological ‘constant’: if every choice entrains predictability and predictability is a measurable variable, then each choice can be related to every other choice in a measurable way; because choice is the way in which individuals consciously interact with their environments and one another, predictability can be used as a ‘common ground’ to measure and compare cases of choice-based sociodynamics.