Unlike the seventeenth-century rationalists such as René Descartes, Baruch Spinoza, and Gottfried Wilhelm Leibniz, John Locke bases his philosophical understanding of the acquisition of knowledge on the concept of empiricism. Where rationalists believe that knowledge is innate to human beings and that thinking hard about things in nature results in learning about reality, empiricists argue that the principal source of knowledge is sensory perception. Locke rejects the rationale that ideas are implanted in the minds of humans at birth.
Locke believes that when humans are born, they have no knowledge. In his famous Essay Concerning Human Understanding, he asserts,
All Ideas come from Sensation or Reflection.
Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas:—How comes it to be furnished? Whence comes it by that vast store which the busy and boundless fancy of man has painted on it with an almost endless variety? Whence has it all the MATERIALS of reason and knowledge? To this I answer, in one word, from EXPERIENCE.
Locke adopts the concept of tabula rasa from the Latin meaning “blank slate.” In his view, children are born with minds akin to a blank sheet of paper, and as they develop, experience becomes the pen that imprints ideas into their minds. He sees knowledge coming from experience in two ways: through the senses and through “reflexion.” He does not suggest that the brain is simply a depository of thoughts but that it is an organ used to organize and analyze the knowledge acquired empirically.
It would be inaccurate to state that Jean-Jacques Rousseau developed his philosophical principles based on Locke’s theories, but he was undoubtedly influenced by them. Rousseau was an Enlightenment thinker who probably had the greatest influence on Immanuel Kant and his theories on ethical thought.
In his Profession of Faith of the Savoyard Vicar, Rousseau introduces a new perspective on thinking. He opines that there is a proper way to view the universe and that it is to reject the notion that humans are at the center of all things. With an empirical eye, like Locke, he states that humans must observe the universe from the periphery or the outside boundaries looking inward. In an attempt to discover his own purpose in life, Rousseau focuses on his moral duties as a human being. He does not reject reason or sensory perceptions but argues that they might not result in truth. The knowledge people learn from those approaches are not necessarily moral. He postulates that “Conscience is the voice of the soul; the passions are the voice of the body.” Human conscience reveals the truth or falsity of what people reason out or sense.
Rousseau places great emphasis on feelings and emotions with respect to thinking and learning, which was theory that was neither acceptable in the Enlightenment era nor in modern philosophical thought. Despite his enormous influence on political theory with propositions still followed today, his philosophical theories on the acquisition of knowledge are universally rejected.