I have existentialist leanings and see myself as a humanist. As a Christian I have had a problem reconciling these three philosophies…

…Thank you for making the attempt. I like it. My question
concerns Paul Tillich’s critic of pure existentialism, stating that
our use of language is universal and points to essentialism. He argues
that Christianity is comprises a dynamic between essentialism and
existentialism. You need both. You can’t separate the two. Is it
really possible to state existence proceeds essence when we worship a
universal Christ, historically grounded? Hope you can make sense of my
confused thoughts. – Eric

Here’s the short version of the answer: Christian existentialism must be understood as distinct from the more familiar atheist existentialism of a Sartre or Camus. I would describe it as follows: In (and only in) the context of a relationship with God through Christ, no essential constraints of law, morality or identity are absolutely binding.

So in atheist existentialism, your existential freedom is absolute, but in Christian existentialism, it is your relationship with God that is absolute, and your existential freedom stems from that relationship. You can look at is as a recasting of the classic Christian belief that servitude to Christ is freedom from the world –i.e. “My yoke is easy…”

Hope that helps. My response is original, but heavily influenced by Kierkegaard, particularly “Fear and Trembling”.