This universe is the `best' of all possible worlds : a tentative reconstruction of the metaphysical system of Leo Apostel

After presenting Apostel's views on scientific realism, I present definitions of the concepts of ontology and metaphysics. I then proceed to develop Apostel's basic ontology and his metaphysics. Apostel proposed a particular understanding of existence based on his views on causation. He also developed a view of the universe as a causal self-explaining system. I discuss and illustrate three kinds of what he calls 'metaphysical deductions' that aim to deliver such a view of the universe. The most important one is the Leibnizian variational method, that should allow us to deduce the existing universe as the 'best' of all possible worlds