A foreshadowing of a new element produced by thought life itself emerges in St. Augustine (354–430). This element soon vanishes from the surface, however, to continue unnoticeably under the cover of religious conception, becoming distinctly discernible again only in the later Middle Ages. In St. Augustine, the new element appears as if it were a reminiscence of Greek thought life. He looks into the external world and into himself, and comes to the conclusion: May everything else the world reveals contain nothing but uncertainty and deception, one thing cannot be doubted, that is, the certainty of the soul's experience itself. I do not owe this inner experience to a perception that could deceive me; I am in it myself; it is, for I am present when its being is attributed to it.
One can see a new element in these conceptions as against Greek thought life, in spite of the fact that they seem at first like a reminiscence of it. Greek thinking points toward the soul; in St. Augustine, we are directed toward the center of the life of the soul. The Greek thinkers contemplated the soul in its relation to the world; in St. Augustine's approach, something in the soul life confronts this soul life and regards it as a special, self-contained world. One can call the center of the soul life the “ego” of man. To the Greek thinkers, the relation of the soul to the world becomes problematic, to the thinkers of modern times, that of the “ego” to the soul. In St. Augustine, we have only the first indication of this situation. The ensuing philosophical currents are still too much occupied with the task of harmonizing world conception and religion to become distinctly aware of the new element that has not entered into spiritual life. But the tendency to contemplate the riddles of the world in accordance with the demand of this new element lives more or less unconsciously in the souls of the time that now follows. In thinkers like Anselm of Canterbury (1033–1109) and Thomas Aquinas (1227–1274), this tendency still shows itself in such a way that they attribute to self-supportive thinking the ability to investigate the processes of the world to a certain degree, but they limit this ability. There is for them a higher spiritual reality to which thinking, left to its own resources, can never attain, but that must be revealed to it in a religious way. Man is, according to Thomas Aquinas, rooted with his soul life in the reality of the world, but this soul life cannot know this reality in its full extent through itself alone. Man could not know how his own being stands in the course of the world if the spirit being, to which his knowledge does not penetrate, did not deign to reveal to him what must remain concealed to a knowledge relying on its own power alone. Thomas Aquinas constructs his world picture on this presupposition. It has two parts, one of which consists of the truths that are yielded to man's own thought experience about the natural course of things. This leads to a second part that contains what has come to the soul of man through the Bible and religious revelation. Something that the soul cannot reach by itself, if it is to feel itself in its full essence, must therefore penetrate into the soul.
Thomas Aquinas made himself thoroughly familiar with the world conception of Aristotle, who becomes, as it were, his master in the life of thought. In this respect, Aquinas is, to be sure, the most prominent, but nevertheless only one of the numerous personalities of the Middle Ages who erect their own thought structure entirely on that of Aristotle. For centuries, he is il maestro di color che sanno, the master of those who know, as Dante expresses the veneration for Aristotle in the Middle Ages. Thomas Aquinas strives to comprehend what is humanly comprehensible in Aristotelian method. In this way, Aristotle's world conception becomes the guide to the limit to which the soul life can advance through its own power for him. Beyond these boundaries lies the realm that the Greek world conception, according to Thomas, could not reach.
Therefore, human thinking for Thomas Aquinas is in need of another light by which it must be illuminated. He finds this light in revelation. Whatever was to be the attitude of the ensuing thinkers with respect to this revelation, they could no longer accept the life of thought in the manner of the Greeks. It is not sufficient to them that thinking comprehends the world; they make the presupposition that it should be possible to find a basic support for thinking itself. The tendency arises to fathom man's relation to his soul life. Thus, man considers himself a being who exists in his soul life. If one calls this entity the ego, one can say that in modern times the consciousness of the ego is stirred up in man's soul life in a way similar to that in which thought was born in the philosophical life of the Greeks. Whatever different forms the philosophical currents in this age assume, they all hinge on the search for the ego-entity. This fact, however, is not always brought clearly to the consciousness of the thinkers themselves. They mostly believe they are concerned with questions of a different nature. One could say that the Riddle of the Ego appears in a great variety of masks. At times it lives in the philosophy of the thinkers in such a concealed way that the statement that this riddle is at the bottom of some view or other might appear as an arbitrary or forced opinion. In the nineteenth century this struggle over the riddle of the ego comes to its most intensive manifestation, and the world conceptions of the present time are still profoundly engaged in this struggle.
This world riddle already lived in the conflict between the nominalists and the realists in the Middle Ages. One can call Anselm of Canterbury a representative of realism. For him, the general ideas that man forms when he contemplates the world are not mere nomenclatures that the soul produces for itself, but they have their roots in a real life. If one forms the general idea “lion” in order to designate all lions with it, it is certainly correct to say that, for sense perception, only the individual lions have reality. The general concept “lion” is not, however, only a summary designation with significance only for the human mind. It is rooted in a spiritual world, and the individual lions of the world of sense perception are the various embodiments of the one lion nature expressed in the “idea of lion.”
Such a “reality of ideas” was opposed by Nominalists like Roscellin (also in the eleventh century). The “general ideas” are only summary designations for him, names that the mind forms for its own use for its orientation, but that do not correspond to any reality. According to this view, only the individual things are real. The quarrel is characteristic of the specific mentality of its participants. Both sides feel the necessity to search for the validity, the significance of the thoughts that the soul must produce. Their attitude to thoughts as such is different from what the attitudes of Plato and Aristotle were toward them. This is so because something has happened between the end of the development of Greek philosophy and the beginning of modern thought. Something has gone on under the surface of historical evolution that can, however, be observed in the attitude that the individual thinkers take with respect to their thought life.
To the Greek thinker, thought came as a perception. It arose in the soul as the red color appears when a man looks at a rose, and the thinker received it as a perception. As such the thought had the immediate power of conviction. The Greek thinker had the feeling, when he placed himself with his soul receptively before the spiritual world, that no incorrect thought could enter from this world into the soul just as no perception of a winged horse could come from the sense world as long as the sense organs were properly used. For the Greeks, it was a question of being able to garner thoughts from the world. They were then themselves the witnesses of their truth. The fact of this attitude is not contradicted by the Sophists, nor is it denied by ancient Scepticism. Both currents have an entirely different shade of meaning in antiquity from similar tendencies in modern times. They are not evidence against the fact that the Greek experienced thought in a much more elementary, content-saturated, vivid and real way than it can be experienced by the man of modern times. This vividness, which in ancient Greece gave the character of perception to thought, is no longer to be found in the Middle Ages.
What has happened is this. As in Greek times thought entered into the human soul, extinguishing the formerly prevalent picture consciousness, so, in a similar way, during the Middle Ages the consciousness of the “ego” penetrated the human soul, and this dampened the vividness of thought. The advent of the ego-consciousness deprived thought of the strength through which it had appeared as perception. We can only understand how the philosophical life advances when we realize how, for Plato and Aristotle, the thought, the idea, was something entirely different from what it was for the personalities of the Middle Ages and modern times. The thinker of antiquity had the feeling that thought was given to him; the thinker of the later time had the impression that he was producing thought. Thus, the question arises in him as to what significance what has been produced in the soul can have for reality. The Greek felt himself to be a soul separated from the world; he attempted to unite with the spiritual world in thought. The later thinker feels himself to be alone with his thought life. Thus, the inquiry into the nature of the “general ideas” begins. The thinker asks himself the questions, “What is it that I have really produced with them? Are they only rooted in me, or do they point toward a reality?”
In the period between the ancient current of philosophical life and that of modern philosophy, the source of Greek thought life is gradually exhausted. Under the surface, however, the human soul experiences the approaching ego-consciousness as a fact. Since the end of the first half of the Middle Ages, man is confronted with this process as an accomplished fact, and under the influence of this confrontation, new Riddles of Life emerge. Realism and Nominalism are symptoms of the fact that man realizes the situation. The manner in which both Realists and Nominalists speak about thought shows that, compared to its existence in the Greek soul, it has faded out, has been dampened as much as had been the old picture consciousness in the soul of the Greek thinker.
This points to the dominating element that lives in the modern world conceptions. An energy is active in them that strives beyond thought toward a new factor of reality. This tendency of modern times cannot be felt as the same that drove beyond thought in ancient times in Pythagoras and later in Plotinus. These thinkers also strove beyond thought but, according to their conception, the soul in its development, its perfection, would have to conquer the region that lies beyond thought. In modern times it is presupposed that the factor of reality lying beyond thought must approach the soul, must be given to it from without.
In the centuries that follow the age of Nominalism and Realism, philosophical evolution turns into a search for the new reality factor. One path among those discernible to the student of this search is the one the medieval Mystics — Meister Eckhardt (died 1327), Johannes Tauler (died 1361), Heinrich Suso (died 1366) – have chosen for themselves. We receive the clearest idea of this path if we inspect the so-called German Theology (Theologia, deutsch), written by an author historically unknown. The Mystics want to receive something into the ego-consciousness; they intend to fill it with something. They therefore strive for an inner life that is “completely composed,” surrendered in tranquillity, and that thus patiently waits to experience the soul to be filled with the “Divine Ego.” In a later time, a similar soul mood with a greater spiritual momentum can be observed in Angelus Silesius (1624–1677).
A different path is chosen by Nicolaus Cusanus (Nicolaus Chrypffs, born at Kues on the Moselle, 1401, died 1464). He strives beyond intellectually attainable knowledge to a state of soul in which knowledge ceases and in which the soul meets its god in “knowing ignorance,” in docta ignorantia. Examined superficially, this aspiration is similar to that of Plotinus, but the soul constitution of these two personalities is different. Plotinus is convinced that the human soul contains more than the world of thoughts. When it develops the energy that it possesses beyond the power of thought, the soul becomes conscious of the state in which it exists, and about which it is ignorant in ordinary life.
Paracelsus (1493–1541) already has the feeling with respect to nature, which becomes more and more pronounced in the modern world conception, that is an effect of the soul's feeling of desolation in its ego-consciousness. He turns his attention toward the processes of nature. As they present themselves they cannot be accepted by the soul, but neither can thought, which in Aristotle unfolded in peaceful communication with the events of nature, now be accepted as it appears in the soul. It is not perceived; it is formed in the soul. Paracelsus felt that one must not let thought itself speak; one must presuppose that something is behind the phenomena of nature that will reveal itself if one finds the right relationship to these phenomena. One must be capable of receiving something from nature that one does not create oneself as thought during the act of observation. One must be connected with one's “ego” by means of a factor of reality other than thought. A higher nature behind nature is what Paracelsus is looking for. His mood of soul is so constituted that he does not want to experience something in himself alone, but he means to penetrate nature's processes with his “ego” in order to have revealed to him the spirit of these processes that are under the surface of the world of the senses. The mystics of antiquity meant to delve into the depths of the soul; Paracelsus set out to take steps that would lead to a contact with the roots of nature in the external world.
Jakob Boehme (1575–1624) who, as a lonely, persecuted craftsman, formed a world picture as though out of an inner illumination, nevertheless implants into this world picture the fundamental character of modern times. In the solitude of his soul life he develops this fundamental trait most impressively because the inner dualism of the life of the soul, the contrast between the “ego” and the other soul experiences, stands clearly before the eye of his spirit. He experiences the “ego” as it creates an inner counterpart in its own soul life, reflecting itself in the mirror of his own soul. He then finds this inner experience again in the processes of the world. “In such a contemplation one finds two qualities, a good and an evil one, which are intertwined in this world in all forces, in stars and in elements as well as in all creatures.” The evil in the world is opposed to the good as its counterpart; it is only in the evil that the good becomes aware of itself, as the “ego” becomes aware of itself in its inner soul experiences.