Since 1677, the year of publication of the Ethics, Spinoza's ideas have provoked, following a variety of directions, an unceasing interest to this day. However, these ideas have most often been addressed, disconnected from the evidential context that supports their exposition, due to the intensely technical character and the dry style of that context.

This book, which aims to serve as a working tool for those seeking a more immediate access to Spinoza's text, provides all the explanations that are absolutely necessary for reading the first part of the Ethics, in which, under the title "On God," an attempt is made to study reality as a whole, starting from the rational and causal principle that simultaneously endows it with its internal unity and its absolutely necessary character.

This part of Spinoza's book, which due to its relative brevity is particularly difficult and enigmatic, plays an essential role in the overall economy of the Ethics: it is what provides the ethical liberation program with its objective foundation, establishing it deeply within the nature of things.