Meaning: Gottfried Wilhelm Leibniz, a prominent German philosopher and mathematician of the 17th century, made significant contributions to the fields of metaphysics, epistemology, and logic. The quote "This is why the ultimate reason of things must lie in a necessary substance, in which the differentiation of the changes only exists eminently as in their source; and this is what we call God" reflects Leibniz's philosophical views on the nature of reality and the existence of God.

In this quote, Leibniz is expressing his belief in the existence of a necessary substance as the ultimate reason for all things. This necessary substance, according to Leibniz, is the source of differentiation and change in the world. He refers to this substance as "God," linking his philosophical arguments with theological concepts.

Leibniz's philosophy is deeply rooted in the idea of monads, which are indivisible, immaterial, and conscious substances that constitute the fundamental building blocks of reality. These monads, according to Leibniz, are the ultimate constituents of the universe and are characterized by their perceptions and appetitions. In his metaphysical system, Leibniz posits that all changes and variations in the world are the result of the unfolding and interaction of these monads.

The concept of a necessary substance as the ultimate reason for all things can be understood within the framework of Leibniz's principle of sufficient reason. According to this principle, there is an explanation or reason for the existence of everything, and this reason can be found in the nature of a necessary substance, which Leibniz equates with God. In other words, the diversity and complexity of the world can be traced back to the nature of this necessary substance, which provides the reason for the existence and arrangement of all things.

Leibniz's conception of God as the necessary substance aligns with his rationalist approach to metaphysics and theology. He sought to reconcile his philosophical ideas with traditional theological doctrines, presenting a vision of God as the ultimate source of order and harmony in the universe. For Leibniz, God is not only the creator of the world but also the sustaining force that ensures the coherence and intelligibility of the entire cosmos.

Furthermore, Leibniz's emphasis on the necessary substance as the source of differentiation and change reflects his commitment to the principle of continuity. He envisioned a world in which every aspect, from the smallest monad to the entire universe, is interconnected and harmoniously integrated. In this context, the necessary substance serves as the unifying principle that underlies the diverse manifestations of reality.

Overall, Leibniz's quote encapsulates his philosophical stance on the ultimate reason of things and the role of God as the necessary substance. It illustrates his attempt to provide a coherent and rational account of the nature of reality, incorporating metaphysical, theological, and epistemological elements into a comprehensive framework. By exploring the implications of this quote, one gains insight into Leibniz's profound philosophical inquiries and his enduring influence on the history of ideas.