Published online by Cambridge University Press: 28 February 2022
A scientific explanation is prima facie micro-reductive if the explanans refers to the behavior or properties of the micro-parts of something mentioned in the explanandum. Entity x is appropriately regarded as a micro-part of y whenever the following individually necessary and jointly sufficient conditions are satisfied:
(i) x is spatio-temporally contained in y
(ii) for any other part of y, either
a) x is spatio-temporally discrete from it, or
b) x and it are assigned to different “levels”, such that parts from only one level are used in any given micro-explanation,
(iii) x and y. share at least one quantitative, additive property such that
a) the amount of this property attributed to x is less than the amount attributed to y, and
b) the former amount arithmetically contributes to the latter.