<Tr> <Td> Dense things sink . </Td> <Td> It will sink if its density is greater than the density of the fluid . </Td> </Tr> <Tr> <Td> You breathe in oxygen and breathe out carbon dioxide . </Td> <Td> Gas exchange takes place between the air in the alveoli and the blood . </Td> </Tr> <Tr> <Td> Plants get water through their roots . </Td> <Td> Water diffuses through the cell membrane of the root hair cells . </Td> </Tr> <P> Recently, there has been some philosophical interest in the development of a third category of objects known as the quasi-abstract . Quasi-abstract objects have drawn particular attention in the area of social ontology and documentality . It has been argued that the over-adherence to the platonist duality of the concrete and the abstract has led to a large category of social objects having been overlooked or rejected as nonexisting because they exhibit characteristics which the traditional duality between the concrete and the abstract has regarded as incompatible . Specially, the ability to have temporal location, but not spatial location, and have causal agency (if only by acting through representatives). These characteristics are exhibited by a number of social objects, including states of the international legal system . </P>

Which shows these items in order from abstract to concrete