Immanuel Kant, who lived from 1724 – 1804, was the first of the German idealist philosophers. He spent the whole of his life in Königsberg, in East Prussia (now Kaliningrad in Russia). He wrote a “Critique of Pure Reason” and a “Critique of Practical Reason”, published in 1781 and 1786 respectively. He was also the first to suggest that when we look at the Milky Way we see the vertical section of a galaxy.
We have seen, in our previous talk, that the British empiricists held that our ideas are derived from sense experience. At the same time, Kant read in Hume that we cannot know about universal laws of nature from experience, because we cannot know that the sun will rise tomorrow. Kant, however, who had a great admiration for the science of Newton, was sure that it is possible to know laws of nature. Mathematics and physics, for example, state universal laws. If we cannot know them a posteriori, that is after experience, as Hume held, then it must be a priori. Before Kant, ideas were thought to be either analytic (contained in the subject by definition) and a priori or a posteriori and synthetic. Kant, however, thought that there could be synthetic ideas which are not known a posteriori but a priori, and his Critique of Pure Reason could be said largely to be an attempt to show the possibility of synthetic a priori ideas.
An example of something that is known a priori but synthetic is Newton’s first law: a moving body continues to move in a straight line at a constant speed unless another force acts on it. This is not known a posteriori because it has never been observed as there always is another body in the universe acting on it; so we know it a priori.
Thus Kant came to think that not all our ideas are derived from experience, as the Empiricists had held. Indeed, he thought that sensations and impressions do not by themselves constitute experience but require ideas in order to turn them into intelligible experience. As these ideas must precede experience they cannot be known from it a posteriori but be a priori. Thus Kant introduced a so-called revolution into the way we view the world. Just as Copernicus taught us not to think that the heavens revolve round the earth but, on the contrary, the earth goes round the sun, so Kant proposed that our ideas are not based on the structure of the world but the way we see the world is conditioned by ideas that come from our mind. These are Kant’s synthetic a priori ideas or categories of thought, which are the ways that we consider and talk about objects and include the ideas of quantity (one or many), quality, unity (when a thing is seen as a whole), substance (when considered as a subject of qualities and change), and relation (for example, as cause and effect).
How could Kant show that these ideas do not come from things but first from our minds? Let us take the idea of substance, which Hume dismissed as a mere chimera but Kant thought was required to explain any experience. First, how can we know that the phenomena or appearances we observe are of one and the same object: for example, the crescent and full circle shapes we observe in the sky on successive clear nights are all of one object, the moon? If we cannot know this, astronomy can make little progress. Kant thought there must be something permanent which relates all the varying phenomena. He also thought there must be something permanent which relates the phenomena because changes are often gradual; so what causes the change must have a continued existence, in other words, be a substance.
The first substance I know about is myself. In order to have experience at all the subject which perceives many impressions, has thoughts and memories, must possess identity and continuity, and so be a substance. There is no unity of experience without a permanent subject of my experiences, thoughts and memories. My present and future thoughts and actions can only be explained by my past thoughts and actions if I am a permanent subject. But what sort of substance am I? Am I a body, a soul, or a self? Kant preferred to talk about my “I”, but this “I” is an immaterial substance, because it is not known by the senses but by reflection. Thus the starting-point of Kant’s philosophy is subjective: it is my “I”, not the world around me, because with every thought and perception I have goes the thought “I am thinking, perceiving this”. But as my body is part of the material world and my “I” is an immaterial substance, Kant perpetuated the dualism of Descartes. This led Kant into a dilemma, which he expressed in his Third Antinomy: How can my actions be free when they are performed by my body that is part of the natural world which Kant, in accordance with the prevailing scientific view of the 18th century, thought to be determined. On the other hand, “I” am the originator of my actions and my “I” is not part of the world bound by the laws of nature as it is an immaterial substance. It was a false dilemma because I am bound by the laws of chess how I can move a piece, say a knight, but I freely choose the way I move it each time within the rules. Unless our actions are in part limited by the laws of nature, I could not direct my actions at a goal, say direct an arrow to a target. There is no incompatibility between laws of nature and freedom.
To go back to how Kant thought we have experience. He thought that we have two faculties: sensibility and understanding: experience comes about through the interaction of the two. The senses deliver impressions to intuition, as Kant called it, and the a priori ideas which come from the understanding arrange our sense impressions into an intelligible order. You will see from this that, in Kant, we do not so much discern order in the world but impose our own order on the world, so that we only know the world as we represent things to ourselves with the ideas of our mind. This might seem to be a rather subjective view of the world. Kant could have replied that our view of the world is not purely subjective (each person has his or her own view) but objective because everyone agrees about the ideas that condition our view of the world and, secondly, we cannot think of a world in which these ideas do not apply.
It followed for Kant that as we only know things as we represent them to ourselves, we cannot know things in themselves but only phenomena. Thus Kant laid it down that our categories of thought (substance, cause, etc.) only apply to objects known by the senses, and hence only to phenomena. As we do not know God or the soul by the senses and they have no phenomena, we cannot show that they exist: we are not permitted to go beyond “the bounds of sense”. This, however, was not the end of Kant’s thoughts about God and the soul.
Although I have now reached the time limit I have set myself for each of these talks, if you will allow me just three more minutes, I shall show you how Kant, having concluded in the Critique of Pure Reason that we cannot know that God, the soul and freedom exist, then found in the Critique of Practical Reason that he required all three to make sense of the moral law.
Kant thought that we have a duty to obey the moral law, but there is no such thing as obedience without freedom. Moreover, we cannot be moral beings unless we have free will. But in order to be free, Kant thought that we must be completely autonomous. We are not autonomous if the law that we must obey is imposed on us from outside. Therefore, the moral law does not come from God but we must each be the author of the moral law. This, however, did not mean that Kant thought that we were free to do what we liked. Quite the contrary, there was one constraint, which Kant called the “categorical imperative”, which applies to everything I want to make a law for myself: I should so act that whatever I chose could be made into a universal law for everyone else to obey. So, if I do not want anyone else to deceive me by lying or breaking promises, I should not deceive others myself.
It followed for Kant that, as I am autonomous (literally, follow my own law), everyone else enjoys an equal autonomy and, therefore, we should not use anyone as a means towards our own ends, for each person is an end in himself or herself. We should not exploit others, and slavery is excluded. This is a noble thought in Kant but it does not follow, because I should not treat anybody as a means to my own ends, everyone is an end in himself or herself. The end of everyone is God.
Kant thought we had a duty to promote the highest good, which is happiness. Happiness, Kant thought, lay in the harmony of our wills with nature but, as we are not the cause or author of nature, the connection between morality and happiness cannot be grounded in our reason. The ground of this connection must therefore be the cause of nature, which as it follows laws must be an intelligent being, consequently God. Kant also thought that there is endless progress towards this harmony of our will with the moral law even beyond this life. Endless progress of course required the immortality of the soul.
Thus Kant found himself constrained to bring back God, the soul and freedom by the back door, so to speak. It seems to me, however, we have little reason to act as though God, the soul and freedom existed because the moral law requires them (unless we know that they exist). If Kant could properly hold that they are postulates of practical reason, he should also have admitted that we can after all know that God, the soul and freedom exist.