Mereology - (from the Greek μερος, ‘part’) is the theory of parthood relations: of the relations of part to whole and the relations of part to part within a whole.
Nelson Goodman - american philosopher, known for his work on mereology & irrealism.
Mereology and Buddhism: Mereological Dependence in Buddhist Philosophy
Top-down implies bottom-up
In Engaging Buddhism page 33, Jay Garfield points out that in Buddhist philosophy mereological dependency works both ways:
"As a consequence of the rejection of the ultimate existence of infinitesimal parts, the dependence relation between parts and wholes came to be recognized as a two-way street. Given that there is no ultimate decomposition of wholes into parts, the identification of any part as a part came to be seen as a matter of decompositional interest, just as the identification of a condition as an explanans is seen as dependent upon explanatory interests. For something to exist as a part of a whole, on this view, is to be dependent on the whole in two respects. First, if the whole does not exist, the part does not exist as the kind of thing it is when it figures in the whole.
To take Wittgenstein's example in Philosophical Investigations, a brake lever is only a brake lever, and not simply a metal rod, in the context of a car in which it so functions (§6). A biological organ, such as a heart, depends on an entire organism to develop, to function and to be an organ at all.
Second, decomposition can be accomplished in many ways. We might say that a memory chip is a part of a computer if we are decomposing it functionally, and that the parts of the chip are circuits, and so on. On the other hand, we might decompose the computer into adjacent 1 mm cubes, in which case the chip might turn out to be involved in several different parts, and not to be a part itself. If the whole in question is a solid volume, the cubes are parts; if it is a computer, the chip is a part, and 1 mm cubes are irrelevant. So, just as wholes depend on their parts, parts depend on their wholes."
"Things, Mereology and Schemes" - Art by Leon Ka - (his Instagram stream)
"Leon Ka / aka Kafre (b. Barcelona, Spain 1980) is a Ph.D. student at Universitat de Barcelona with a dissertation on Metaphysical Relations: Ontological Dependence and Metaphysical Implication as well as a street artist that uses his art to make visual these seemingly abstract and esoteric concepts."