Kierkegaard might be mystified by the current form of existentialism.
From his philosophical and psychological Christian apologetics to the
post-WWII existentialists, existentialism has betrayed its roots by
attempting to embrace logic as its foundation. A reading of "Being and
Nothingness," the foremost text on existentialism, shows that leading thinkers,
such as Sartre, try to sanitize and package existentialism to a general
public shackled by intellectualism.

With his wry cynicism of reason, Kierkegaard might remind even the
"weekend philosophers" that the dichotomy between logic and existence
cannot be breached. Attempts to "proove" existentialism through logic
should be dismissed as incomplete. Criticism based only on reason is equally
unacceptable.

That is not to say that existentialism is infallible and/or unprovable, or does
it? This question is a matter for another post...