Pure numbers and “natural” laws (such as the law of gravity) demonstrate that thoughts and ideas are not illusions. They exist, even though they are not composed of matter and are not merely the results of material changes in a human brain. Demonstrating that the material world also is not an illusion seems more difficult. Who can show, beyond all doubt, that all of us and the world around us are not the contents of someone’s dream? Or, in a more modern approach, who can show that we are not elements in a computer-generated simulation of reality rather than existing in reality itself?
Already ancient philosophers suggested that the most real of real things are thoughts or ideas. We use the word “table” to identify pieces of furniture that have a similar design and function, even though the tables we experience can be different heights, sizes, colors, and be made of different materials. The same can be said of the words “tree” and “dog.” Other philosophers answer that “table” and “tree” and “dog” are merely invented labels, words that have no meaning apart from the way we use them to categorize real things. This assertion becomes more difficult when we analyze immaterial concepts such as “beauty” and “justice” and “love.” Not only are those ideas real; they impart reality by existing within the items or actions we notice happening in us and in the world around us.
Many thinkers describe a world in which “mind over matter” expresses the philosophy of idealism. Some claim that a positive mental attitude can bring about healing and prosperity. Others point to logical inconsistencies in the material world which we seem to inhabit. Dreams, hallucinations, pareidolia (such as seeing animal shapes in clouds or faces in abstract designs), and illusionists (Doug Henning and David Copperfield, for example) all warn us that the world we perceive might not be the world that truly exists. Many prominent philosophers have taught idealism, speaking against the philosophies of materialism and dualism.
One problem with idealism, from a practical level, is that the world does not always conform to what our minds believe. I trip over a table in the dark because my mind did not think it was there and did not expect it to be there. More significantly, ideas are shared from one mind to another through material means of communication—largely through sight (the printed word) and sound (the spoken word). Idealism seems to falter when offering a comprehensive view of our world. George Berkeley suggested that all material objects are formed by ideas, but that their reality rests in the mind of God. For that reason, we might encounter material objects we did not expect, because God’s mind upholds their reality. This answer appeals no less than the assertion that God has created a material world which is upheld by his power but which is as real as any mind or spirit created by God and depending upon God for its existence.
Immanuel Kant distinguished between the phenomena which we perceive and the noumena which cause those phenomena. All we can know is the phenomena, the perceptions which reach us through our senses. The noumena, the causes of those phenomena, are unknowable. They are as likely to be immaterial ideas as they are to have any material form. Kant would have been fascinated with more recent explorations into subatomic particles. Physicists have found that the raw ingredients of matter are very different from the world we perceive—they do not even follow the rules of Euclid’s geometry and Newton’s physics. Kant would say to all of us today, “I told you so!”
Dualism has many advocates among modern philosophers. Some twentieth century materialists conceded the reality of ideas, but they went on to say that the nonmaterial ideas were not part of a different world that overlaps the material world but has its own rules. Instead, they said that nonmaterial ideas exist as the material world seen in a different way. One example given by those philosophers is the university. One can show a visitor to the university the buildings and grounds, the professors and students and administration and staff, the books and papers and scientific equipment. Has the visitor then seen the university? It exists in all those things, yet it is none of those things. It is an idea that coexists within those things; but it could not exist without those things being present.
A second example would be a sport like baseball. One can show a visitor a bat and ball and glove. One can show a ballpark. One can introduce the visitor to baseball players, managers, coaches, and umpires. One can hand over a rulebook and invite the visitor to read the rules of the game. In the end, the visitor has not seen baseball until that visitor has witnessed part of a baseball game. The game is the real idea of baseball. Its existence, in a way, is beyond any of the elements of the game; yet baseball would not exist without the equipment and players and rulebook.
Given that approach to dualism from a materialist approach, the human mind and soul can be said to exist, to be real, but their reality still depends upon the material existence and survival of the human body and brain. God could be said to exist, but only as a Mind or Spirit that inhabits the material universe and needs that universe for His existence and survival.
A contrary spin on dualism begins with God, a Spirit who has no material form, but Who creates matter and everything that consists of matter. His creation is not an illusion; the material world exists, but it relies upon its Creator for continued existence and survival. Time and space are ideas created by God, as are human minds and spirits and—potentially—other spiritual beings created by the same God. This form of dualism, acknowledging the reality of the material world but making its existence dependent on the spiritual reality, best fits the traditional beliefs and teachings of Christians, Jews, and Muslims. J.