Rea's 1997 book, Material Constitution: A Reader, is an anthology of 17 articles on the problems of coincident entities, contingent identity, mereological nihilism, and problems of identity,

In 2008, he compiled the five-volume anthology Metaphysics: Critical Concepts in Philosophy, with 98 articles by modern metaphysicians covering all areas of metaphysics. His 2104 book Metaphysics: the basics, is an introductory textbook.

Rea's 2002 book, World without Design: The Ontological Consequences of Naturalism, is strongly anti-naturalist, arguing that scientific research amassing knowledge on the basis of experimental evidence choosing between various theories is nothing but a "secular faith." Epistemically, Rea thinks science is no better than a religion.

His five-volume anthology has a convenient chronological table of its articles (from the 1908 McTaggart article on A-time and B-time, to a 2007 article by Thomas Crisp on presentism). Its introduction has a challenging list of metaphysical questions, a surprising number of which may yield to the approach of information philosophy.

Michael Rea	Information Philosopher
When two things share a common property, is there some single identical thing that they in fact share (perhaps as a common part), or is talk of 'sharing' just a manner of speaking? And if there is some actual thing that is shared, then what does the sharing amount to? Is it a kind of overlap, or is it a resemblance?	The shared thing is always a subset of the information in each thing. It need not be material. It is a resemblance. Statements of identity between two things should be paraphrased as "these two things are identical in some respect." They are only the same if we ignore their differences. But any two things are similar if we ignore all their differences, just as they are completely different if we ignore their similarities. The quantifiable information in any physical object far exceeds the amount that is picked out by human perceptions, conceptions, or intentions of what the object might be or might become for our purposes.
When you talk about ways things could have been (e.g. 'there's more than one way this class could turn out'), to what sorts of things (if any) does the word 'ways' refer?	The 'ways' are alternative possibilities for what might happen in the future, some of which become actual. It is these possible actions that let the libertarian say correctly "I could have done otherwise." 'Ways' may also refer to the idea of "possible worlds," in which counterfactual 'ways' are imagined for the events in our world.
What is the relation between an object and its properties? Are the properties of a thing parts or constituents of it? If not, then are we supposed to imagine that properties are somehow external to the things that have them, and are related to them simply by resemblance or some other sort of relation?	The properties of a concrete material object that we see are not themselves material constituents. They are abstract forms that inform us, the arrangement and shape of the material. If the object were shapeless, sheer chaos or noise, we could not distinguish any properties. The properties are in some sense external, outside, on top of, beyond, the material object that has them. The relation is a semblance. It allows our perception to discriminate the differences and the resemblances to other things that we are acquainted with.
Is change really possible? If so, what does it mean to say that something has changed?	Although change may be simply the loss or gain of material, changes are always changes in the information about an entity, for example, its position in space as a function of time, or its form, its internal information.
Is the passage of time possible? And what is time, anyway?	The four dimensions of space and time are an immaterial coordinate system that allows us to keep track of material events, the positions and velocities of the fundamental particles that make up every body in the universe
What does it take to get the members of a set of objects to compose something?	If it is not a proper part of the set of things, our minds must impose an arbitrary form that distinguishes the selected members as a composite object.
Do familiar count nouns (like 'table' and 'chair') actually refer to things, or are they disguised plural referring expressions like 'the Notre Dame football team' or 'the crew of the Enterprise'!	The team and the crew consist of individual members that are countables - people. The table and chairs consist of more or less continuous material - wood or metal, which are mass nouns. To be sure, all continuous material can ultimately be analyzed into a quantifiable number of elementary material particles, but we do not usually describe masses with quantifiers like each, every, several.
What is an event? Can the same event happen more than once? What is involved in one event causing another?	Events are seen as occurring at a particular point in space and time. Events can only have a causal relation to affect events (by exerting physical forces) in the forward light cone of the future.
What are human minds? Are they immaterial thinking substances, or are they material objects (brains, perhaps), or something else entirely?	The human mind is the processing of immaterial information by the material brain. Minds are physical processes, but not another kind of substance, as Descartes thought. The mind-body dualism is not a substance dualism. It is a property dualism, the original and great dualism of idealism and materialism.
Are human beings free? Is freedom even possible?	It is the existence of immaterial alternative possibilities that ensures freedom of the will.
Is it possible to live after death?	No. But some of us may have information immortality.
Do human beings or human faculties have anything like a proper function? Why are there contingent beings rather than none? Is there a necessary being (a God, perhaps) who created all contingent things?	There is a cosmic creation process working in the universe that has produced everything of value, all the information structures - the galaxies, stars, and planets - and information processing systems like human beings. Thinkers pondering this providential force have anthropomorphized it as a benevolent agency. Nothing material is necessary, certain, a priori, or analytic.

Rea saw all these problems could be grouped together under a single problem of material constitution.

What I intend to show is that there is one problem underlying these four familiar puzzles (and their many variants).This problem I will call "the problem of material constitution." I say it underlies the four puzzles for the following reason: every solution to the problem of material constitution is equally a solution to each of these four puzzles, though not vice versa.

("The problem of material constitution." The Philosophical Review, 104(4), 525.)

Rea saw five assumptions at the core of each of the puzzles.

Informally, they are: (i) there is an F and there are ps that compose it, (ii) if the ps compose an F, then they compose an object that is essentially such that it bears a certain relation R to its parts, (iii) if the ps compose an F, then they compose an object that can exist and not bear R to its parts, (iv) if the ps compose both a and b, then a is identical with b, and (v) if a is identical with b then a is necessarily identical with b. Let us call these assumptions, respectively the Existence Assumption, the Essentialist Assumption, (with apologies to Frankfurt) the Principle of Alternative Compositional Possibilities (or PACP for short), the Identity Assumption, and the Necessity Assumption.

("The problem of material constitution." The Philosophical Review, 104(4), 527.)

The most flawed assumption, from an information philosophy point of view, is the identity assumption, especially the idea that material constitution is identity. This assumption, which dates from the pre-Socratics, was challenged by the Stoics, especially by Chrysippus' puzzling description of Dion and Theon.

Dion/Theon is best interpreted as an attack on the Growing Argument, which the Academic Skeptics used to challenge the Stoic claim that their "peculiarly qualified individuals" can survive material change. The Stoics accepted the ancient claim that a change of material causes an object to cease to exist and a new "numerically distinct" object comes into existence.

But the Stoics argued that this sort of material change should be called generation and destruction, since they transform the thing from what it is into something else. This is the Heraclitean philosophy of Becoming, that all is in flux, you can't step into the same river twice. If everything is always changing its material, what is to constitute its Parmenidean Being, especially a human being?

The Academic Skeptic version of the Growing Argument was that matter is the sole principle of individuation, so that a change of matter constitutes a change of identity.

But according to the Stoics, material change is not growing. Something that grows and diminishes must subsist. It must retain its identity over time. Otherwise we cannot say that "it" is growing.

For the Stoics, what comes into existence, grows, then diminishes and dies, is the peculiarly qualified individual (ἰδίος ποιὸν) that is coincident with a different amount of matter from time to time.

But material constitution is not identity, individuals are not their material substrate (ὑποκείμενον), but their unique qualities, which we can take to be Aristotle's immaterial form.

The Stoics have therefore rejected matter as the principle of individuation.