OntologyOntology asks the question “what is there?” Eliminative materialism claims that nothing exists but material particles, which makes many problems in ancient and modern philosophy difficult if not insoluble. To be sure, we are made of the same material as the ancients. With every breath we take, we inspire 10 or 20 of the fixed number of molecules of air that sustained Aristotle. We can calculate this because the material in the universe is a constant, conserved quantity. But information is not a fixed quantity. The stuff of thought and creativity, information has been increasing since the beginning of the universe. It is also the question of ontology. What exists in the world? Ontology is intimately connected with epistemology - how can we know what exist in the world? The ontological status of abstract concepts is a completely different question from the ontology of concrete physical objects, though these questions have often been confounded in the history of philosophy. Information philosophy provides distinct answers to these two ontological questions. Physical objects are pure material or particles of energy that exist in the world of space and time. Abstract concepts (like redness) are pure information, neither matter nor energy, although they need matter for their embodiment and energy for their communication. For example, the abstract idea of two is embodied in two objects. The idea of a circle is embodied in a round object. Redness is embodied in the red photons being emitted or reflected from an object. The arrangement of material objects, whether continuous matter like the wood in a table top, or the momentary position of billiard balls, is pure information. The ancients sometimes said that these abstract concepts do not “exist,” but rather are said to “subsist.” Information philosophy claims that the “form” of an object can not be separated from the matter and so deserves to be ontological. The contrast between physical objects and abstract concepts can be illustrated by the difference between invention and discovery. We discover physical objects through our perceptions of them. To be sure, we invent our ideas about these objects, their descriptions, their names, theories of how they are structured and how they interact energetically - with one another and with us. But we cannot arbitrarily invent the natural world. We must test our theories with experiment. The experimental results select those theories that best fit the data, the information coming to us from the world. This makes our knowledge of an independent external world scientific knowledge. By contrast, we humans invent many abstract concepts such as the names we give to objects. We know that these cultural constructs do not exist somewhere in nature as physical structures before we create them. Cultural knowledge is relative to and dependent on the society that creates it. However, some of our invented abstract concepts seem to clearly have an existence that is independent of us, like the numbers and the force of gravity. Consider the shape of a given object. The abstract representation of the shape in the mind, or in a computer model, is (quantitatively) much less information than the total information in the shape of the physical object. But when the representation is accurate, it is isomorphic with a proper subset of the information in the object itself. We can assert that at least the same information is in the world and should be included in our ontology. The “axiom of independent reality” claims that “Knowledge unconditionally presupposes that the reality known exists independently of the knowledge of it, and that we know it as it exists in this independence.” (H. A. Prichard.) The British empiricists John Locke and David Hume argued that what we are “given” in our perceptions of sense data is limited to so-called “secondary qualities.” These are properties that produce the sensations in the observer’s senses - color, taste, smell, sound, and touch. Knowledge that comes from secondary qualities does not provide objective facts about things “in themselves.” Immanuel Kant described these secondary qualities as “phenomena” that could tell us nothing about the “noumena,” which the empiricists called the “primary qualities.” These are properties the objects have that are independent of any observer, such as solidity, extension, motion, number and figure. These qualities exist in the thing itself (Kant’s “Ding an sich”). Kant thought that some of these qualities can be determined with certainty, as “synthetic a priori” truths. Some of these qualities are analytic truths, defined by the logical meanings of linguistic terms. For example, a round circle cannot be a square. But information philosophy can claim that extension and figure, for example, are both in the object and in our information representation.