New series: philosophical concepts and debates I don't sufficiently understand

I have come to realise that there are many philosophical notions with which I need to be more familiar--at least familiar enough so as not to lose my way in conversations in which they feature. I'm going to learn about them, hopefully at a rate of roughly one a week, then write a short post about each, for the usual reasons.

This post functions as a table of contents for the series of posts:

• A- and B- theories of time
• epistemic defeaters
• semantic entailment
• supervenience
• the hypothetico-deductive method
• the grounding relation
• covariance
• jointly necessary/sufficient conditions
• conditioning on a variable
• non-backtracking counterfactuals
• ethical particularism
• functional explanation
• theory theory
• propositional attitudes/dispositional theory
• alief
• contractualism/contractarianism
• Buridan's ass cases
• internal/external reasons