Such a catalogue of the sorts of things reality contains does not settle all the questions metaphysicians attempt to answer. Consider the claim that there are both mental and physical things. This claim does not settle the issue of whether everything is of the same fundamental kind or not. Monists hold that everything, is of the same fundamental kind or not. Idealists hold that the physical world is mental, that everything, including physical objects such as mountains, is mental.
Materialists hold that everything including any mental entities is physical.
One principle metaphysicians often appeal which seems to support monism is Ockham's razor, which states that entities should not be multiplied beyond necessity. We said that metaphysics attempts to say what reality contains and to analyse the concepts we use to think about it. Note that the task of saying what reality contains, such as causally related events, is different from the task of analysing the concepts we use to think about reality, such as the concept of causation. P.F. Strawson distinguished two sorts of metaphysics. Descriptive metaphysics describes the way we actually think about reality.