In regards to persons, there have been two main questions in the realm of contemporary philosophy: a synchronic question and a diachronic question. The synchronic question deals with the question: “What is a person at a time?” But the diachronic question deals with personal identity over time: “In virtue of what conditions is a person, P1, at t1, the same person, P2, at t2?’ To answer the above questions of persons, I begin by discussing what the core of personhood is. I defend the idea that the core of personhood is having the property of reflexive self-consciousness. Reflexive self-consciousness is having the ability of the act of conceiving oneself as oneself through the act of reflection. Having reflexive self-consciousness is both a necessary and sufficient condition for being a person. By having reflexive self-consciousness a conscious being has the features that are uniquely ascribed to a person, i.e. being a moral agent, being a rational agent and having freedom of action. To have reflexive self-consciousness is to have the ability of entertaining second-order ‘I’-thoughts regarding first-order ‘I’-thoughts.These are, in fact, metacognitive thoughts. Then I discuss the necessary and sufficient conditions for having reflexive self-consciousness. The conditions that are individually necessary and jointly sufficient for having the ability to entertain second-order ‘I’-thoughts ― having reflexive self-consciousness ― are having the three following conditions: 1) the ability to entertain ‘I’-thoughts; 2) the ability for re-identifying the constituents of mental states by the conscious being; 3) being in an intersubjective space. Only those conscious beings that are social beings are able to acquire reflexive self-consciousness. To acquire reflexive self-consciousness a conscious being must be aware that there is a third-person perspective of itself. This is only possible through being in relationships with other conscious beings in an intersubjective space. This leads us to the point that being a person is not an intrinsic property of a conscious being. Drawing upon the outcomes of my discussion of reflexive self-consciousness, I argue that persons are distinct entities from their conscious bodies. Persons and their conscious bodies are of different ontological kinds, though they are not numerically different. Also, persons are not substantially different from their bodies, that is, if a conscious body is a material entity, then the body’s person is a material entity too. The distinction between persons and their conscious bodies, I conclude, is neither one of conceptual distinction nor is a real one. To name this kind of distinction, we can employ the term ‘formal distinction.’ I argue that Baker’s constitution theory can explain the relationship between persons and their bodies at a time. A person is a constituted entity who is constituted by the interaction between a living body and a society. By discussing the notion of ‘derivatively having property,’ I propose a notion of constitution which is compatible with the idea that persons and their bodies are of different ontological kinds and the distinction between the two is one of formal distinction. To answer the question: “What kind of entity is a person?” I argue that persons are consciousness-dependent entities. It follows that a person through time is a stream because consciousness over time is a stream. Persons over time are in fact events that are constituted by their bodies. A body ― in the biological sense ― is an entity that undergoes the event of ‘living.’ Persons are constituted entities that extend over time and that cannot be reduced to their bodies. To answer the diachronic question of persons, I suggest expanding the constitution theory from a static definition to a dynamic definition. ‘Life’ is an event and the stream of consciousness is an event too. Therefore, reflexive self-consciousness is an event. Persons are constituted events who remain the same through time while they undergo change. This idea faces none of the standard problems associated with other views proposed in the philosophical literature regarding the problem of personal identity over time. Simple views of personal identity over time lead us to the idea of substance dualism in regards to the relationship between persons and their bodies. But the theory of persons as constituted events does not imply substance dualism.Understanding persons as constituted events entails that if conscious bodies are material entities, then persons are material too. The complex views of personal identity over time entail the ‘fission problem’ according to which it is possible that a person at t1 is identical to two different persons at t2. The theory of persons as constituted events does not entail the fission problem because, according to this idea, persons are distinct entities from their bodies.