How could any mediaeval thinker look upon Being as ‘the concept most abstract and most empty of content’? To the mentality of the age, untouched by Idealism, Being in some way included everything. Nothing could be added to it, neither difference nor accident. It included all its differences. In this sense the mediaeval philosophers interpreted Aristotle’s doctrine that Being is not a genus. Unlike a generic concept, Being for these thinkers did not decrease in content according to its increase in extension. Besides enjoying the widest possible extension, it possessed in one way or another the greatest possible comprehension. It was far from being an ‘empty’ concept.
J. Owens, The doctrine of being in the aristotelian Metaphysics, p. 3-4.