| Summary | Two characteristics distinguish quantities from non-quantitative properties and relations. First, every quantity is associated with a class of determinate “magnitudes” or “values” of that quantity, each member of which is a property or relation itself. So when a particle possesses mass or charge, it always instantiates one particular magnitude of mass or charge -- like 2.5 kilograms or 7 Coulombs. Second, the magnitudes of a given quantity (alternatively, the particulars which instantiate those magnitudes) exhibit “quantitative structure”, which comprises things like: ordering structure, summation/concatenation structure, ratio structure, directional structure, etc. We often represent quantities using similarly-structured mathematical entities, like numbers, vectors, etc. Classic debates about quantities concern attempts to give a metaphysical account of quantitative structure without appealing to mathematical entities/structures. Other questions include: How do quantities play the roles they do in measurement, the laws of nature, etc? Are a quantity's magnitudes fundamentally absolute (like 2.5 kilograms) or comparative (like twice-as-massive-as)? |