If one were to make a list of iconoclastic and radical thinkers, Benedict Spinoza (1632- 1677) would rank high. His great and enduring work, Ethics, continues to have renewed impact, currently among environmentalists and ecologically minded thinkers. Spinoza wrote numerous philosophical, political, and religious criticism works. His efforts consistently express a mind set in favor of religious tolerance and in opposition to traditional religious orthodoxy. In his two major works, Tractatus Thologico-Politicus and Ethics present interpretations of spiritual concepts that continue to offend some religious believers and provide an avenue of belief for those who aver traditional religion.
Spinoza's Ethics is a remarkable work in two regards:
First, it is written in an unusual style - patterned after Euclid's Geometry with Definitions, Axioms, and Propositions. The definitions are stipulated definitions of key terms used in the work. These definitions do not purport to explain ordinary uses of the words, only to specify how they are being used in the present text.
The axioms are statements about the key terms and are given as self-evident.
The propositions are statements that follow from the definitions, axioms and other propositions.
The result is a text that provides all of its own evidence. Every statement in the book has a clearly identified set of arguments (proofs) given for it. Sometimes when you read a technical or old text, the very language can be a challenge to overcome. With Spinoza, the main technical terms are explicitly defined. The challenge of Ethics is to follow the lines of thought directly and grasp how each point is constructed from the foundations laid in the definitions and axioms.
The second remarkable aspect of Ethics is the striking conclusions Spinoza derives in it. Most of the work revolves around his conception of God
See Def.III above for the term "substance" and Def.IV for the term "attribute." Put all these together, and you have a concise picture of Spinoza's concept of God. This is significant because by his system of proofs, Spinoza derives the following conclusions (among others):
There can only be one substance in existence. That substance is God and everything that exists is part of that substance. God is nature.
God has infinite attributes, of which only two, thought and spatial extension can be known by us. The universe that we apprehend is but a limited portion of the whole.
This leads from an investigation of the structure of reality to practical propositions about how we should think about life and how we may best live it.
Human beings are in a state of bondage, so long as they act solely from emotions.
Freedom can be attained by understanding out own emotional processes and rationally conforming to the conditions of human existence - an acceptance of the world as it is.
On the one hand, Spinoza's reasoning builds a case against popular religion (e.g. Christianity, Judaism, Islam) as a mere reflection of human imagination. On the other hand, Spinoza's philosophy is constructive of an alternate spiritual view. The picture of God/Nature as a whole system of which we individual humans are parts, is an attractive idea for many.