There is an ontological problem associated with defining what it means to be a "person." Being a human person could mean having the capacity for a specific range of intentional states, and intentionality is here defined as object-directedness or object-aboutness. John Searle distinguishes between three kinds of intentionality: original, derived, and metaphorical aboutness. A thought could be intentional insofar as it is about one's beloved or one's consciousness might be directed toward--or be about--God.
It's also possible that the capacity for self-referentiality adequately defines personhood (i.e., I have the ability to think and reference myself by using a first-person singular pronoun); however, persons are also constituted by relations (according to Kevin Corcoran).
One traditional definition of personhood has also been "individual substance of a rational nature" (Boethius, et al). But it seems that this definition of "person" might not work unless one nuances the definiens. What does it mean to be an individual, to be a substance, and to be or have a rational nature? Is it possible to consider babies as persons based on this classical definition?
Maybe another defining criterion that we could suggest for the word "person" is incommunicability. That is to say, a person is unique or cannot be reproduced without loss of personhood (i.e., cloning). One's own personhood is not something that can be shared or communicated.
Whatever a suitable definition of "human person" turns out to be, it seems that a Christian must view personhood through the lens of Genesis 1:26.