Baruch Spinoza (1632–1677) was a Dutch philosopher who was a key rationalist, who saw the underlying unity in the universe.
He was critical of religious scriptures and promoted a view that the Divine was in all, and the Universe was ordered, despite its apparent contradictions. In his work “Ethics” he opposed the mind-body dualism of Descartes.
Inter alia, he was said to have said:
All things excellent are as difficult as they are rare.
Do not weep; do not wax indignant. Understand.
The highest activity a human being can attain is learning for understanding, because to understand is to be free.
If you want the present to be different from the past, study the past.
The world would be happier if men had the same capacity to be silent that they have to speak.
I do not know how to teach philosophy without becoming a disturber of established religion.