Thanks for your email.
Ontological categories? There are numerous ways to approach the question of what they are, why they are significant. As with many other questions there is not just no single answer... there is no immediate answering or knowing. You read and think and live and integrate/reject and the process goes on and in the end you discover that you know something you did not know. Philosophers puzzle why it should be so and call it the "truth that can be shown and not said." But it is not a puzzle from all points of view. Knowing is more than knowing in words, even pictures. Knowledge, including the unconscious - the language of which is also unconscious, reaches down into the rhythm of life and the body. Words - extended discourses pretending to represent all knowing are pointers... a phase of knowing... so what of ontology? God does not need ontology. Ontology is the truth of the way things are, the one thing is... ontology is the way. The categories represent the best [in some sense - the intellectual senses] in understanding of the way...
Chron's disease... why am I interested in it? Marta has it. It is an autoimmune disorder in which the body attacks itself. Mainly, the attack is in the digestive tract but it could be anywhere. And it can be life threatening. When Marta was 18 she was told she had, maybe, a few years to live. Fall of 1999, she was in UCSF hospital for weeks [insurance payed out in excess of $1000,000] and life and death were in balance. She told friends to contact me, somehow they neglected to do that. Anyway when she was told she had only a few years to live, she lived that way... but when she was 26 she realized she was still alive and might as well live as though she was going to live the normal life span.