B Idealism and Skepticism

B

Idealism and Skepticism

Efforts to resolve the dualism of mind and matter, a problem first raised by Descartes, continued to engage philosophers during the 17th and 18th centuries. The division between science and religious belief also occupied them. There, the aim was to preserve the essentials of faith in God while at the same time defending the right to think freely. One view called Deism saw God as the cause of the great mechanism of the world, a view more in harmony with science than with traditional religion. Natural science at this time was striding ahead, relying on sense perception as well as reason, and thereby discovering the universal laws of nature and physics. Such empirical (observation-based) knowledge appeared to be more certain and valuable than philosophical knowledge based upon reason alone.

After Locke philosophers became more skeptical about achieving knowledge that they could be certain was true. Some thinkers who despaired of finding a resolution to dualism embraced skepticism, the doctrine that true knowledge, other than what we experience through the senses, is impossible. Others turned to increasingly radical theories of being and knowledge. Among them was German philosopher Immanuel Kant, probably the most influential of all because he set Western philosophy on a new path that it still follows today. Kant’s view that knowledge of the world is dependent upon certain innate categories or ideas in the human mind is known as idealism.

B1

Leibniz

Gottfried Wilhelm Leibniz

The 17th-century thinker Gottfried Leibniz made contributions to a variety of subjects, including theology, history, and physics, although he is best remembered as a mathematician and philosopher. According to Leibniz, the world is composed of monads—tiny units, each of which mirrors and perceives the other monads in the universe.

German philosopher Gottfried Wilhelm Leibniz, like Spinoza before him, worked in the rationalist (reason-based) tradition to produce a brilliant solution to the problems raised by dualism. Leibniz, a mathematician and statesman as well as a philosopher, developed a remarkably subtle and original system of philosophy that combined the mathematical and physical discoveries of his time with the organic and religious conceptions of nature found in ancient and medieval thought. Leibniz viewed the world as an infinite number of infinitely small units of force, called monads, each of which is a closed world but mirrors all the other monads through its activity, which is perception. All the monads are spiritual entities, but they can combine to form material bodies. Leibniz conceived of God as the Monad of Monads, which creates all other monads and predestines their development.

Leibniz’s theory of the predestination of monads, also called the theory of preestablished harmony, entailed a radical rejection of causality—the view that every effect must have a cause. According to Leibniz, monads do not interact with each other at all, and the appearance of mechanical causality in the natural world is unreal, akin to an illusion. Likewise, there is no room in the universe for free will: Even though we enjoy the illusion of acting freely, all human actions are predetermined by God. Despite these gloomy conclusions, Leibniz’s philosophy was profoundly optimistic because he argued that ours was the best of all possible worlds. He based this belief on considerations about the nature of truth and necessity. French writer Voltaire mocked this viewpoint in Candide (1759), a satirical novel that examines the woes heaped on the world in the name of God.

B2

Berkeley

George Berkeley

Irish philosopher George Berkeley is considered the founder of idealism, the philosophical view that all physical objects are dependent on the mind for their existence. According to Berkeley's early 18th-century writings, an object such as a table exists only if a mind is perceiving it. Hence, objects are ideas.

In the 18th century Irish philosopher and Anglican churchman George Berkeley, like Spinoza before him, rejected both Cartesian dualism and the assertion by Hobbes that only matter is real. Berkeley maintained that spirit is substance, and that only spiritual substance is real. Extending Locke’s doubts about knowledge of an external world, outside the mind, Berkeley argued that no evidence exists for the existence of such a world, because the only things that we can observe are our own sensations, and these are in the mind. The very notion of matter, he maintained, is incoherent and impossible. To exist, he claimed, means to be perceived (“esse est percipi”), and in order for things to exist when we are not observing them, they must continue to be perceived by God. By claiming that sensory phenomena are the only objects of human knowledge, Berkeley established the view known as phenomenalism, a theory of perception that suggests that matter can be analyzed in terms of sensations.

B3

Hume

David Hume

Scottish philosopher David Hume is considered one of the greatest skeptics in the history of philosophy. Hume thought that one can know nothing outside of experience, and experience—based on one’s subjective perceptions—never provides true knowledge of reality. Even the law of cause and effect was, for Hume, an unjustified belief: If one drops a ball, one cannot be certain it will fall to the ground. Rather, it is only possible to recognize through past experience that certain pairs of events (dropping a ball, the ball striking the ground) have always accompanied one another.

Whereas Berkeley argued against materialism by denying the existence of matter, 18th-century Scottish philosopher David Hume questioned the existence of the mind itself. Hume’s skeptical philosophy also cast doubt on the idea of cause as understood in all previous philosophies and seriously disputed earlier arguments for the existence of God. His most important philosophical work, A Treatise of Human Nature, was published in three volumes in 1739 and 1740.

All metaphysical assertions about things that cannot be directly perceived are equally meaningless, Hume claimed, and should be “committed to the flames.” In his analyses of causality and induction, Hume revealed that there is no logical justification for believing that any two events which occur together are connected by cause and effect or for making any inference from past to future. Hume noted that we depend on our past experience whenever we form beliefs about anything that we do not directly perceive and whenever we make predictions about the future. According to the empiricist doctrine of Bacon, Locke, and Berkeley, we can do this because experience teaches us what particular things belong together as causes and effects. Hume, however, argued that this attempt to learn from experience is not at all rational, thus calling into question the reliability of our memories, our reasoning processes, and our ability to learn from past experiences or to make even the smallest predictions about the future—for example, that the sun will rise tomorrow. Though extreme, Hume’s skepticism about philosophical empiricism raised problems about the possibility of knowledge that contemporary philosophers still struggle to resolve.

B4

Kant

Immanuel Kant

Eighteenth-century German philosopher Immanuel Kant explored the possibilities of what reason can tell about the world of experience. In his critiques of science, morality, and art, Kant attempted to derive universal rules to which, he claimed, every rational person should subscribe. In Critique of Pure Reason (1781), Kant argued that people cannot understand the nature of the things in the universe, but they can be rationally certain of what they experience themselves. Within this realm of experience, fundamental notions such as space and time are certain.

German philosopher Immanuel Kant was among the first to appreciate Hume’s skepticism, and in response he published the Critique of Pure Reason (1781), widely considered the greatest single work in modern philosophy. In this work Kant made a thorough and systematic analysis of the conditions for knowledge. As an example of genuine knowledge, he had in mind the contributions to physics of English scientist Isaac Newton. In the case of Newtonian physics, reason seemed to have done an effective job of understanding the data supplied by the senses and to have succeeded in postulating universal and necessary laws of nature, such as the law of gravitation and the laws of motion. Kant proposed to explain how such knowledge is possible, thereby providing a complete reply to Hume’s skepticism and answering many of the problems that had plagued Western philosophers since the time of Descartes.

Kant started by making a fresh analysis of the elements of knowledge, asking for the first time an extremely basic question, “How is our experience possible in the first place?” Kant’s predecessors had taken experience for granted. Thus Descartes agreed that we seem to have sensory knowledge of the world but asked whether this knowledge was true or the result of a dream. Similarly, Hume’s skepticism about causation arose when he concluded that we do not encounter causality in our ordinary experience of the world and that any inferences about it, beyond immediate experience, were questionable. Kant’s answer to the skepticism of Descartes and Hume involved certain categories, such as space, time, substance, and causality, which he maintained are essential to our thinking and to our experience of phenomena in the world. These categories he called transcendental. All objects of our knowledge, he concluded, must conform to the human mind’s essential ways of perceiving and understanding—ways that involve the transcendental categories—if they are to be knowable at all. Kant maintained that he had developed a revolutionary hypothesis about knowledge and reality that he believed to be as significant for the future of philosophy as the hypothesis of Copernicus—that the planets orbit the Sun—had been for science.

Kant’s claim that causality, substance, space, and time are forms imposed by the mind gave support to the idealism of Leibniz and Berkeley. Kant, however, made his view a more critical form of idealism by granting the empiricist claim that things-in-themselves—that is, things as they exist outside human experience—are unknowable. Kant therefore limited knowledge to the “phenomenal world” of experience, maintaining that metaphysical beliefs about the soul, the cosmos, and God (the “noumenal world” transcending human experience) are matters of faith rather than of scientific knowledge.

In his ethical writings Kant held that moral principles are categorical imperatives, absolute commands of reason that permit no exceptions and are not related to pleasure or practical benefit. Kant argued that human beings should act as members of an ideal “kingdom of ends” in which every person is treated as an end in himself or herself, and never as a means to someone else’s ends. In addition, everyone should govern their conduct as if their actions were to be made law—a law that applies equally to all without exception. Kant thereby postulated a freedom of action based on moral order and equality. His moral philosophy contributed to modern political ideas about freedom and democracy. Kant was a leading figure of the movement for reason and liberty against tradition and authority, and in his religious teachings he emphasized individual conscience and represented God primarily as a moral ideal.

Kant’s writings constituted a high point of the Enlightenment, a fertile intellectual and cultural period that helped stimulate the social changes that produced the French Revolution (1789-1799). Other leading thinkers of this movement included Voltaire, Jean Jacques Rousseau, and Denis Diderot. Voltaire, developing the tradition of Deism begun by Locke and other liberal thinkers, reduced religious beliefs to those that can be justified by rational inference from the study of nature. Rousseau criticized civilization as a corruption of humanity’s nature and developed Hobbes’s doctrine that the state is based on a social contract with its citizens and represents the popular will. Diderot published a 35-volume work known as the Encyclopédie to which many scientists and philosophers contributed. Diderot and his Encyclopedists, as they were known, associated the progress and the happiness of humankind with science and knowledge, whereas Rousseau criticized such ideas along with the very notion of civilization.