Being is being in a situation, and thus is always changing. Being is transcendent, it transcends objective enquiry. Our own experience of Being is subjective. Thus, ontological enquiry can be engaged in only by taking intersubjectivity as a starting point. We are part of, and thus cannot be objective about, our own existence.
Existence transcends objective enquiry, and is thus a mystery.
Scientific questions can be presented to us as problems for which there can be solutions. But philosophic questions are centered on the study of mystery. Philosophy cannot find solutions to questions which cannot be formulated as problems. Philosophy is thus a mode of enquiry, rather than a problem-solving activity. Marcel distinguishes between problems and mysteries.