The problematic relationship between science and philosophy has, since the beginning of modernity, divided the world into two separate domains: nature and human. Some of today's schools of philosophy and epistemological inquiry have maintained a radical separation to the point where they refuse to maintain any commonality within the two. We argue that such a dichotomy will not only destroy the idea of the unity of knowledge from a theoretical perspective but, it will destroy a unified understanding of reality. This article is a critique of now mainstream belief of such dichotomy through re-reading of Leibniz's idea on the unity of knowledge. The distinctive feature of Leibniz's approach, which was specifically laid down in his correspondence with Clarke, is that his way of reasoning is philosophical as well as physical. In Leibniz's view what guarantees the soundness of philosophical principles cannot defy the laws of physics. We shall also demonstrate that Chaos Theory is consistent with the affinities of Leibniz's approach. The main focus of this article is on re-evaluating views on causal determinism and randomness as well as free will. The final claim of this article is that the natural world and human world follow the same causal deterministic laws, and that causal laws are however nonlinear. Knowledge of our reality should be rigorously sought in both the domains of humanities and natural sciences, but this causal determinism should distance itself from a simple linear causal model. What is thought of as random events or probabilistic events in the physical world, as well as in the human world, are not ontologically run by chance. The complexity and vastness of reality are such that our knowledge of reality always suffers a lack, and it is this lack of knowledge that is usually being called randomness.