Rene Descartes (1596-1650) was a French philosopher and mathematician. Considered the "father of modern philosophy" Descartes developed many ideas that lead to the creation of many modern fields of study. As a mathematician he developed concepts that linked algebra and geometry which eventually led to the evolution of calculus.
He was the first to write of the concept of emotions and his famous quotation "I think therefore I am" elucidated his focus on the importance of cognition on the human experience. In psychology Descartes is most known for his concept of dualism. Descartes' theory of dualism suggests that there are two realms to existence. The first is the physical realm which is the environment and the things around us. This is the "realm of matter and energy". This realm can be researched and is scientific because it operates in a prescribed "mechanical" way. The other realm is mental and is "transcendent" to the physical environment and cannot be measured.
Dualism allowed for the separation of sciences and the non-physical realm, which was important long ago because it allowed scientists to conduct their research without fear of being considered heretics by religious groups. Dualism creates a problem for psychologists and the study of the mind: psychologists can ignore the mind entirely and view behavior as purely mechanical or include the mind in study but it not be considered "scientific".
As for mathematics, Descartes devised “deductive reasoning” which may be applied in various sciences. He is also known for the “method of normals”, a procedure in calculus for identifying normal and tangent lines to curves; and “Cartesian geometry”, the use of a coordinate system in studying geometry.
As a scientist, some of his contributions include “Balloonist theory”, a neuroscience concept which asserts that muscle contraction may be caused by air or fluid inflation; and “conservation of momentum,” a Newtonian mechanics concept which explains that the momentum of an object is the product of its mass and velocity.
As for his early life, his mother died when he was a year old so he was left in the care of his maternal grandmother and then later on by his great uncle. Descartes enjoyed a modest rank of nobility as his father, Joachim Descartes, was a member of the “Parlement of Brittany”. Following his father’s wishes, he graduated with a degree and license in canon and civil law. However, his ambition was actually to become a professional military officer so he studied military engineering in which he was able to work on mathematics and physics concepts such as conic section, free fall, and fluid statistics.
Descartes had a daughter, Francine, as a fruit of his relationship with a servant girl, Helena Jans van der Strom, in Amsterdam. However, she died at the young age of 5 due to scarlet fever. Unlike his contemporary moralists, Descartes acknowledged the importance of emotions and openly wept upon his daughter’s death.
Descartes’ works had become famous in Europe by 1649 and Sweden’s Queen Christina invited him to organize a scientific academy and to tutor her about love. Their classes were supposedly scheduled at five in the morning and it was speculated that the cold weather led to Descartes’ contraction of pneumonia. He passed away on February 11, 1650.