by Ulf Wolf
Descartes further believed that by following his rationalist method, one could establish first principles (fundamental underlying truths) for all knowledge—about man, the world, even about God.
And so—for Descartes was nothing if not ambitious—he resolved to reconstruct all human knowledge on an absolutely certain (mathematical) foundation by refusing to accept any belief, even the belief in his own existence, until he could prove it absolutely true.
As an example of his approach—in his so-called “dream argument”—he asserted that our inability to prove with certainty when we are awake and when we are dreaming makes most of our knowledge uncertain.
Ultimately he concluded that the principal thing about which one can be certain is oneself as a thinking being. This conclusion forms the basis of his well-known argument: Cogito, ergo sum—”I think, therefore I am.”
Here one can, and—from a Buddhist standpoint—should, introduce an important counter-argument: “I think not, therefore I am not.” Descartes took a subtle though enormous leap of faith when he assumed that just because thinking is perceived that there is a specific entity, or a person—in other words, an I—that perceives it. This is not necessarily the case.
Be that, though, as it may. Back to Descartes. From this conclusion he went on to argue that, in pure thought, one can have a clear conception of God and can in fact demonstrate that God exists. In fact, he held that it was this secure knowledge of the reality of God that allowed him to harbor his earlier doubts about knowledge and science.
Despite his mechanistic outlook, however, Descartes accepted the traditional religious doctrine of the immortality of the soul and maintained that mind and body are two distinct substances, thus exempting mind from the mechanistic laws of nature and providing for freedom of the will.
His fundamental separation of mind and body, known as dualism, raised the problem of explaining how two such different substances as mind and body can affect each other, a problem he was unable to solve and one that has remained a conundrum for philosophy (and religion, not to mention science) ever since.
Hobbes
One attempt to solve this riddle was made by the 17th–century English philosopher Thomas Hobbes (1588-1679). In his effort to attain unity, he asserted that matter is, in fact, the only real substance, and that mind does not really exist.
Based on this postulate, he constructed a comprehensive system of metaphysics that provided a solution to the mind-body problem by reducing mind to the internal motions of the body—a view that still is very popular in scientific circles.
Spinoza
Whereas Hobbes tried to oppose Cartesian dualism by reducing mind to matter, the 17th-century Dutch philosopher Baruch Spinoza (1632-1677) attempted to reduce matter to mind—to divine spiritual substance.
To achieve this, Spinoza constructed a precise system of philosophy that offered new solutions to the mind-body problem and to the now increasingly brewing conflict between religion and science.
Not unlike Descartes, Spinoza postulated that all of nature, her entire structure, can be deduced from a few basic definitions and axioms, on the model of Euclidean geometry. However, Spinoza believed that Descartes’s theory of two substances created an insoluble problem of the way in which mind and body interact, and so concluded that the ultimate substance is God and that God, substance, and nature are identical.
Thus he supported a pantheistic view that all things are simply varying aspects of God.
Spinoza’s solution to the mind-body problem addressed the apparent interaction of mind and body by seeing them as two forms of the same substance, which exactly parallel each other, thus only seeming to affect each other but in truth do not.
Spinoza’s bases his ethics, much like Hobbes, on a materialistic psychology where individuals are motivated only by self-interest—leading, for the most part to guaranteed conflict. But in contrast to Hobbes, Spinoza concluded that rational self-interest can, and often does, coincide with the interest of others—avoiding, for the most part, such conflict.
Locke
John Locke (1632-1704) also addressed Cartesian dualism, but he held the more commonsense view that the corporeal (bodily or material) and the spiritual are simply two parts of nature that are, by design, always present in human experience. Beyond that, he made no attempt to define these parts of nature or to construct a detailed system of metaphysics in an attempt to explain them.
In fact, Locke believed that such philosophical aims were impossible to carry out and would lead no-useful-where.
In contrast to the rationalism of Descartes and Spinoza—who both believed that knowledge could be achieved through pure reason and logical deduction—Locke carried on the empiricist tradition founded by Bacon and later embraced by Hobbes: knowledge is derived from observation and sense perceptions, and not from reason alone.
In 1690, with the publication of his Essay Concerning Human Understanding, Locke gave his empirical view a systematic framework.
In this essay, Locke attempted, and in many respects succeeded, to steer philosophy away from the study of the physical world and toward the study of the human mind, and as a result made epistemology—the study of the nature of knowledge—the principal concern of philosophy in the 17th and 18th centuries.
In his theory of the mind, Locke held that all ideas are but simple elements of experience, but he did distinguish sensation from reflection as sources of experience: sensation, he maintained, provided the material for knowledge of the external world, while reflection provided the material for knowledge of the mind.
Locke were to greatly influence later British thinkers, such as George Berkeley and David Hume, by calling attention to the vagueness of metaphysical concepts and that inferences about the world outside the mind cannot be truly proved.
Idealism and Skepticism
Efforts to resolve the dualism of mind and matter—the problem raised by Descartes—was still alive and well, and continued to engage philosophers through the 17th and 18th centuries.
Philosophy during these centuries also grew increasingly concerned about, and occupied with, the still relatively new division between science and religious belief; mostly with the aim of preserving the essentials of faith in God while at the same time defending the right to think freely.
Natural science, meanwhile, strode ahead, relying on sense perception and reason to discover ever more universal laws of nature and physics. Such empirical knowledge appeared more certain and valuable than philosophical knowledge based upon reason alone and so, on the religious side, gave rise to Deism, a view that saw God as the cause of the great mechanism of the world and therefore more in harmony with science than with traditional religion.
After Locke, however, philosophers grew increasingly skeptical about gaining knowledge that they could be absolutely 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 the German philosopher Immanuel Kant (see below), probably the most influential of all because he set Western philosophy on a new path—idealism—that philosophers travel to this day.
Leibniz
Leibniz (1646-1716), who like Spinoza before him was a true rationalist, produced a brilliant theoretical solution to the problems raised by dualism. He devised a subtle philosophical system that combined the mathematical and physical discoveries of his time with the organic and religious concepts of nature found in ancient and medieval thought.
Leibniz saw the world as an infinite (i.e., limitless) number of infinitely small (i.e., extremely small but smaller) units of force, called monads, each of which he postulated as a closed world that yet mirrored all other monads.
He further held that all monads were spiritual entities that could combine to form material bodies. To Leibniz, God was the Chief Monad, the one who created
all other monads and predestined their development.
However, Leibniz’s theory of the predestination of monads—which is still known as the theory of pre-established harmony—entailed a radical rejection of causality, the view that every effect must have a cause, for according to Leibniz, monads never interact with each other, and any appearance of causality in the natural world is unreal, an illusion.
And Leibniz didn’t stop there. He also held that there is no room in the universe for free will. Even though we enjoy the illusion of acting freely, he said, all human actions are in fact predetermined by God.
God, in other words, is the only one responsible for everything, humanity can wash its hands of any wrong (or right-) doing.
Berkeley
The 18th-century Irish philosopher George Berkeley, like Spinoza before him, rejected both Cartesian dualism and the assertion by Hobbes that only matter is real. Berkeley struck out in the opposite direction (and all the way, at that) by maintaining that spirit is, in fact, substance, and that only spiritual substance is real.
Then, expanding upon 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, claimed Berkeley, means to be perceived, and in order for things to exist when we are not perceiving them, they must (at all times) be perceived by God.
Hume
Whereas Berkeley argued against materialism by outright denial of matter, 18th-century Scottish philosopher David Hume (1711-1776) took the next step by questioning the existence of the mind itself.
Hume’s skeptical philosophy also cast serious doubt on the idea of cause as a factor understood in all previous philosophies and also seriously disputed earlier arguments for the existence of God.
All assertions—whether physical or metaphysical—about things that cannot be directly perceived here and now, are equally meaningless, Hume claimed, and should, as he put it, be “committed to the flames.”
In his somewhat myopic analyses of causality and induction, Hume steadfastly maintained that there is no logical justification for believing that any two events which occur in sequence are in any way connected by cause and effect or for making any inference from past to future.
Hume went on to note that while we pretend to 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, we do this because experience teaches us what particular things belong together as causes and effects.
However, he then went on to argue 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.
Anybody who drinks too deeply from the chalice of Hume will spend a long time trying to rediscover his feet.
Kant
German philosopher Immanuel Kant (1724-1804) actually appreciated Hume’s skepticism, and in response to it, in 1781, he published the Critique of Pure Reason, widely considered the greatest single work in modern philosophy, wherein he made a thorough and systematic analysis of the conditions for knowledge.
As an example of genuine knowledge, he cited Newton’s contributions to the laws of physics. In the case of Newtonian physics, Kant argued, reason seemed to have done an effective job of comprehending and categorizing the data supplied by the senses, and based on them to have succeeded in postulating universal and necessary laws of nature, such as the law of gravitation and the laws of motion.
Kant explained how such knowledge could in fact be possible, and so provided a complete reply to Hume’s skepticism and also answered many of the problems that had plagued Western philosophers since the time of Descartes.
Kant set out 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 concluded that certain categories of knowledge, such as space, time, substance, and causality—all of which he maintained are essential to our thinking and to our experience of phenomena in the world—should be viewed as transcendental. Therefore, he concluded, all objects of knowledge 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, not particularly modest by leaning, proclaimed that his newly developed hypothesis about knowledge and reality was as significant for the future of philosophy as the hypothesis of Copernicus—that the planets orbit the Sun—had been for science.
He then, however, went on to claim that things-in-themselves—that is, things as they exist outside human experience—are unknowable, and so managed to limit human knowledge to the “phenomenal world” of experience. Metaphysical beliefs about the soul, the cosmos, and God (the “noumenal world” transcending human experience), Kant held, are matters of faith, and can never be perceived or proven.
Some maintain (a view not shared by yours truly) that Kant’s musings constituted a high point of the Enlightenment.
19th Century Philosophy
Kant was, in fact, so revered that the 19th–century philosopher generally developed his views with reference to his understanding of Kant.
In Germany, Kant’s influence led subsequent philosophers to explore idealism and ethical voluntarism, a philosophical tradition that places a strong emphasis on human will. While philosophers before Kant had explored the objects of knowledge, those who followed him on the path of idealism turned to the subject of knowledge—what some have since referred to as the ego, or the I, the mind, and human consciousness.
First came Johann Gottlieb Fichte (1762-1814), who transformed Kant’s critical idealism into absolute idealism by eliminating Kant’s “things-in-themselves” (external reality) and by making the self, or the ego, the ultimate reality.
Fichte held that the world is, in fact, created by an absolute ego, which is conscious first of itself and only later of non-self, or the otherness of the world.
The human will, he maintained, a partial manifestation of self, gives human beings freedom to act.
Friedrich Wilhelm Joseph von Schelling (1775-1854) stepped even closer to absolute idealism by construing objects or things as the works of the imagination and Nature as an all-embracing being, spiritual in character.
Schelling thus went on to became the leading philosopher of the Romantic movement, which in contrast to the Enlightenment placed its faith in feeling and the creative imagination rather than in reason.
This romantic view of the divinity of nature influenced the American transcendentalist movement, led by poet and essayist Ralph Waldo Emerson, and pursued by others like David Henry Thoreau.
Hegel
Some view Georg Wilhelm Friedrich Hegel (1770-1831) as the most powerful philosophical mind of the 19th-century, and for good reason.
His system of a nearly absolute idealism, although influenced greatly by Kant and Schelling, was based on his own conception of logic and his own philosophical method.
In fact, and contrary to the skeptics, Hegel believed that absolute truth, or reality, exists and that the human mind can know it—a very positive view indeed.
This is so, he maintained, because “whatever is real is rational.” He conceived the subject matter of philosophy to be what reality as a whole actually consisted of, a reality he named Absolute Spirit, Cosmic Reason.
The world of human experience, whether subjective or objective, is but a manifestation of Absolute Spirit.
Philosophy’s task, according to Hegel, is to trace and chart the path of Absolute Spirit from its original abstract, undifferentiated being into more and m
ore concrete reality.
Hegel believed that this charting occurs by a dialectical process—that is, a process whereby conflicting ideas resolve—consisting of a series of triads. Each triad involves: (a) an initial state (or thesis), which might be an idea or a movement; (b) its opposite state (or antithesis); and (c) a higher state, or synthesis, combining elements from the two opposites into a new and superior arrangement. The new synthesis then becomes the thesis of the next triad in an unending progress toward the ideal.
Unfortunately, Hegel then went on to argue that this dialectical logic should be applied to the advancement of all knowledge, including science and history, where his views were to provide a foundation for the political and social philosophy later developed by Karl Marx.
According to Hegel, human history demonstrates the dialectical development of Absolute Spirit as can be observed in the conflicts and wars, the rise and fall of civilizations. In fact, he maintained that political states are real entities, discrete identities, the manifestation of Spirit in the world, and individual participants of history. In every epoch a particular state is the bearer or agent of spiritual advance, and it thereby gathers to itself power.
Because the dialectic means opposition and conflict, war must be expected, and it has value as evidence of the health of a state.
Hegel’s philosophy did stimulate interest in history by representing it as a deeper penetration into reality than the natural sciences provide.
His conception of the national state as the highest social embodiment of the Absolute Spirit was for some time—and in many quarters still is—believed to be the main source of 20th-century totalitarianism, although Hegel himself, despite his concept of the national state as identity, advocated a large measure of individual freedom.