[1 of 9] Plotinus (c. 204-270, Egypt): primary subject "Senses, limitations of" (search under Cosmology/Science)": source "Plotinus: the Enneads": detail "Section 5.5.1"
Consider sense-knowledge: its objects seem most patently certified, yet the doubt returns whether the apparent reality may not lie in the states of the percipient rather than in the material before him; the decision demands intelligence or reasoning. Besides, even granting that what the senses grasp is really contained in the objects, none the less what is thus known by the senses is an image: sense can never grasp the thing itself; this remains for ever outside. …
 It is thus, I suppose, that in sense-perception we have belief instead of truth; we satisfy ourselves with something very different from the original which is the occasion of perception.

[2 of 9] Plotinus (c. 204-270, Egypt): primary subject "Reality, observations on" (search under Inner Life/Teachings)": source "Cosmic Consciousness": detail "From ‘To Flaccus’ 188: 78-81 [a compilation of Plotinian phrases compiled by R.A.Vaughan in 'Hours with the Mystics']"
External objects present us only with appearances. Concerning them, therefore, we may be said to possess opinion rather than knowledge. The distinctions in the actual world of appearance are of import only to ordinary and practical men. Our question lies with the ideal reality that exists behind appearance. How does the mind perceive these ideas? Are they without us, and is the reason, like sensation, occupied with objects external to itself? What certainty would we then have — what assurance that our perception was infallible? The object perceived would be a something different from the mind perceiving it. We should have then an image instead of reality. It would be monstrous to believe for a moment that the mind was unable to perceive ideal truth exactly as it is, and that we had not certainty and real knowledge concerning the world of intelligence. It follows, therefore, that this region of truth is not to be investigated as a thing external to us, and so only imperfectly known. It is within us. Here the objects we contemplate and that which contemplates are identical — both are thought. The subject cannot surely know an object different from itself. The world of ideas lies within our intelligence. Truth, therefore, is not the agreement of our apprehension of an external object with the object itself. It is the agreement of the mind with itself. Consciousness, therefore, is the sole basis of certainty. The mind is its own witness. Reason sees in itself that which is above itself as its source; and again, that which is below itself as still itself once more.
 Knowledge has three degrees - opinion, science, illumination. The means or instrument of the first is sense; of the second, dialectic; of the third intuition. To the last I subordinate reason. It is absolute knowledge founded on the identity of the mind knowing with the object known.

[3 of 9] Plato (c. 429 - 347 BC, Greece): primary subject "Philosophy, extracts" (search under Inner Life/Mind, Psyche, Soul, Spirit)": detail "The Cave: ‘Republic’ VII 514-519"
Next, said I, compare our nature in respect of education and its lack to such an experience as this. Picture men dwelling in a sort of subterranean cavern with a long entrance open to the light on its entire width. Conceive them as having their legs and necks fettered from childhood, so that they remain in the same spot, able to look forward only, and prevented by the fetters from turning their heads. Picture further the light from a fire burning higher up and at a distance behind them, and between the fire and the prisoners and above them a road along which a low wall has been built, as the exhibitors of puppet shows have partitions before the men themselves, above which they show the puppets.
 All that I see, he said.
 See also, then, men carrying past the wall implements of all kinds that rise above the wall, and human images and shapes of animals as well, wrought in stone and wood and every material, some of these bearers presumably speaking and others silent.
 A strange image you speak of, he said, and strange prisoners.
 Like to us, I said. For, to begin with, tell me do you think that these men would have seen anything of themselves or of one another except the shadows cast from the fire on the wall of the cave that fronted them?
 How could they, he said, if they were compelled to hold their heads unmoved through life?
 And again, would not the same be true of the objects carried past them?
 If then they were able to talk to one another, do you not think that they would suppose that in naming the things that they saw they were naming the passing objects?
 And if their prison had an echo from the wall opposite them, when one of the passers-by uttered a sound, do you think that they would suppose anything else than the passing shadow to be the speaker?
 By Zeus, I do not, said he.
 Then in every way such prisoners would deem reality to be nothing else than the shadows of the artificial objects.
 Quite inevitably, he said.
 Consider, then, what would be the manner of the release and healing from these bonds and this folly if in the course of nature something of this sort should happen to them. When one was freed from his fetters and compelled to stand up suddenly and turn his head around and walk and to lift up his eyes to the light, and in doing all this felt pain and, because of the dazzle and glitter of the light, was unable to discern the objects whose shadows he formerly saw, what do you suppose would be his answer if someone told him that what he had seen before was all a cheat and an illusion, but that now, being nearer to reality and turned toward more real things, he saw more truly? And if also one should point out to him each of the passing objects and constrain him by questions to say what it is, do you not think that he would be at a loss and that he would regard what he formerly saw as more real than the things now pointed out to him?
 Far more real, he said.
 And if he were compelled to look at the light itself, would not that pain his eyes, and would he not turn away and flee to those things which he is able to discern and regard them as in very deed more clear and exact than the objects pointed out?
 It is so, he said.
 And if, said I, someone should drag him thence by force up the ascent which is rough and steep, and not let him go before he had drawn him out into the light of the sun, do you not think that he would find it painful to be so haled along, and would chafe at it, and when he came out into the light, that his eyes would be filled with its beams so that he would not be able to see even one of the things that we call real?
 Why, no, not immediately, he said.
 Then there would be need of habituation, I take it, to enable him to see the things higher up. And at first he would most easily discern the shadows and, after that, the likenesses or reflections in water of men and other things, and later, the things themselves, and from these he would go on to contemplate the appearances in the heavens and heaven itself, more easily by night, looking at the light of the stars and the moon, than by day the sun and the sun’s light.
 Of course.
 And so, finally, I suppose, he would be able to look upon the sun itself and see its true nature, not by reflections in water or phantasms of it in an alien setting, but in and by itself in its own place.
 Necessarily, he said.
 And at this point he would infer and conclude that this it is that provides the seasons and the courses of the year and presides over all things in the visible region, and is in some sort the cause of all these things that they had seen.
 Obviously, he said, that would be the next step.
 Well then, if he recalled to mind his first habitation and what passed for wisdom there, and his fellow bondsmen, do you not think that he would count himself happy in the change and pity them?
 He would indeed.
 And if there had been honors and commendations among them which they bestowed on one another and prizes for the man who is quickest to make out the shadows as they pass and best able to remember their customary precedences, sequences, and coexistences, and so most successful in guessing at what was to come, do you think he would be very keen about such rewards, and that he would envy and emulate those who were honored by these prisoners and lorded it among them, or that he would feel with Homer and greatly prefer while living on earth to be serf of another, a landless man, and endure anything rather than opine with them and live that life?
 Yes, he said, I think that he would choose to endure anything rather than such a life.
 And consider this also, said I. If such a one should go down again and take his old place would he not get his eyes full of darkness, thus suddenly coming out of the sunlight?
 He would indeed.
 Now if he should be required to contend with these perpetual prisoners in ‘evaluating’ these shadows while his vision was still dim and before his eyes were accustomed to the dark — and this time required for habituation would not be very short — would he not provoke laughter, and would it not be said of him that he had returned from his journey aloft with his eyes ruined and that it was not worth while even to attempt the ascent? And if it were possible to lay hands on and to kill the man who tried to release them and lead them up, would they not kill him?
 They certainly would, he said.
 This image then, dear Glaucon, we must apply as a whole to all that has been said, likening the region revealed through sight to the habitation of the prison, and the light of the fire in it to the power of the sun. And if you assume that the ascent and the contemplation of the things above is the soul’s ascension to the intelligible region, you will not miss my surmise, since that is what you desire to hear. But Gods knows whether it is true. But, at any rate, my dream as it appears to me is that in the region of the known the last thing to be seen and hardly seen is the idea of good, and that when seen it must needs point us to the conclusion that this is indeed the cause for all things of all that is right and beautiful, giving birth in the visible world to light, and the author of light and itself in the intelligible world being the authentic source of truth and reason, and that anyone who is to act wisely in private or public must have caught sight of this.
 I concur, he said, so far as I am able.
 Come then, I said, and join me in this further thought, and do not be surprised that those who have attained to this height are not willing to occupy themselves with the affairs of men, but their souls ever feel the upward urge and the yearning for that sojourn above. For this, I take it, is likely if in this point too the likeness of our image holds.
 Yes, it is likely.
 And again, do you think it at all strange, said I, if a man returning from divine contemplations to the petty miseries of men cuts a sorry figure and appears most ridiculous, if, while still blinking through the gloom, and before he has become sufficiently accustomed to the environing darkness, he is compelled in courtrooms or elsewhere to contend about the shadows of justice or the images that cast the shadows and to wrangle in debate about the notions of these things in the minds of those who have never seen justice itself?
 It would be by no means strange, he said.
 But a sensible man, I said, would remember that there are two distinct disturbances of the eyes arising from two causes, according as the shift is from light to darkness or from darkness to light, and, believing that the same thing happens to the soul too, whenever he saw a soul perturbed and unable to discern something, he would not laugh unthinkingly, but would observe whether coming from a brighter life its vision was obscured by the unfamiliar darkness, or whether the passage from the deeper dark of ignorance into a more luminous world and the greater brightness had dazzled its vision. And so he would deem the one happy in its experience and way of life and pity the other, and if it pleased him to laugh at it, his laughter would be less laughable than that at the expense of the soul that had come down from the light above.
 That is a very fair statement, he said.
 Then, if this is true, our view of these matters must be this, that education is not in reality what some people proclaim it to be in their professions. What they aver is that they can put true knowledge into a soul that does not possess it, as if they were inserting vision into blind eyes.
 They do indeed, he said.
 But our present argument indicates, said I, that the true analogy for this indwelling power in the soul and the instrument whereby each of us apprehends is that of an eye that could not be converted to the light from the darkness except by turning the whole body. Even so this organ of knowledge must be turned around from the world of becoming together with the entire soul, like the scene-shifting periactus in the theater, until the soul is able to endure the contemplation of essence and the brightest region of being. And this, we say, is the good, do we not?
 Of this very thing, then, I said, there might be an art, an art of the speediest and most effective shifting or conversion of the soul, not an art of producing vision in it, but on the assumption that it possesses vision but does not rightly direct it and does not look where it should, an art of bringing this about.
 Yes, that seems likely, he said.
 Then the other so-called virtues of the soul do seem akin to those of the body. For it is true that where they do not pre-exist, they are afterward created by habit and practice. But the excellence of thought, it seems, is certainly of a more divine quality, a thing that never loses its potency, but, according to the direction of its conversion, becomes useful and beneficent, or, again, useless and harmful. Have you never observed in those who are popularly spoken of as bad, but smart men how keen is the vision of the little soul, how quick it is to discern the things that interest it, a proof that it is not a poor vision which it has, but one forcibly enlisted in the service of evil, so that the sharper its sight the more mischief it accomplishes?
 I certainly have, he said.
 Observe then, said I, that this part of such a soul, if it had been hammered from childhood, and had thus been struck free of the leaden weights, so to speak, of our birth and becoming, which attaching themselves to it by food and similar pleasures and gluttonies turn downward the vision of the soul — if, I say, freed from these, it had suffered a conversion toward the things that are real and true, that same faculty of the same men would have been most keen in its vision of the higher things, just as it is for the things toward which it is now turned.
 It is likely, he said.
 Well, then, said I, is not this also likely and a necessary consequence of what has been said, that neither could men who are uneducated and inexperienced in truth ever adequately preside over a state, nor could those who had been permitted to linger on to the end in the pursuit of culture — the one because they have no single aim and purpose in life to which all their actions, public and private, must be directed, and the others, because they will not voluntarily engage in action, believing that while still living they have been transported to the Islands of the Blessed?
 True, he said.
 It is the duty of us, the founders, then, said I, to compel the best natures to attain the knowledge which we pronounced the greatest … .

[4 of 9] Maitreya-natha (c. 270-350, Inda): primary subject "Nature, as a reflection of spiritual world" (search under Cosmology/Science)"
When one sees that all objects are reflections of the mind, one abandons the distraction of objectivity.

[5 of 9] Swedenborg (1688-1772, Sweden): primary subject "Nature, as a reflection of spiritual world" (search under Cosmology/Science)": source "Arcana Coelestia, vol.4": detail "Section 3483"
Whatsoever appears anywhere in the universe, is representative of the Lord's kingdom, insomuch that nothing exists anywhere in the ethereal and starry universe, or in the earth and its three kingdoms, but what in its manner and measure is representative. For all things in general and particular which are in nature are ultimate images; for from the Divine proceed the celestial things which are of good, and from these celestial things the spiritual things which are of truth, and from both the former and the latter proceed natural things. Hence it may be evident how gross, yea, how terrestrial, and also inverted, human intelligence is, which ascribes all things to nature separated from, or deprived of, an influx prior to itself, or from an efficient cause. They also who so think and speak, seem to themselves to be wiser than others, in ascribing all things to nature; when yet angelic intelligence consists in ascribing nothing to nature, but all and everything to the Lord's Divine, thus to life, and not to anything dead. The learned know that subsistence is perpetual existence, but nevertheless it is contrary to the affection of falsity, and thereby contrary to, the reputation of learning, to say, that nature continually subsists, as it originally had existence, from the Lord's Divine. Now, since all things in general and particular subsist from the Divine, that is, continually exist, and all things in general and particular which are therefrom cannot be otherwise than representative of those things whereby they came into existence, it follows, that the visible universe is nothing else than a theatre representative of the Lord's kingdom, and that this latter is a theatre representative of the Lord Himself.

[6 of 9] Underhill, Evelyn (1875-1941, England): primary subject "Reality, observations on" (search under Inner Life/Teachings)": source "Mysticism"
But we have no reason to suppose that matter, space, and time are necessarily parts of reality; of the ultimate Idea. Probability points rather to their being the pencil and paper with which we sketch it.

[7 of 9] Nicoll, Maurice (1884-1953, Scotland): primary subject "Reality, observations on" (search under Inner Life/Teachings)"
When we consider that the picture of the world on the retina is two-dimensional and that this is the source of contact with the outer scene, it is not difficult to understand that Kant came to the conclusion that the mind creates the physical world, and lays down the laws of nature, owing to innate dispositions in it that arrange the stream of incoming sensations into an organized system. The senses merely give us messages, and out of these we create the visible, tangible, audible world by some inner action of the mind, by something which is more than the messages. But it is extremely difficult to persuade ourselves that this is so, because in order to do so we must detach ourselves from the overwhelmingly immediate impression of an external reality in which we are invariably immersed.

[8 of 9] Nicoll, Maurice (1884-1953, Scotland): primary subject "Reality, observations on" (search under Inner Life/Teachings)"
We cannot, then, be certain that what we see is the unchallengeable reality of things. If our senses worked in a different way, if we had more senses, or fewer, what we customarily call reality would be different. The matter has been expressed by Kant in many passages, in one of which he says that if ‘the subjective constitution of the senses in general were removed, the whole constitution and all the relation of objects in space and time, nay, space and time themselves, would vanish’. And if our senses were changed the appearance of objects would change, for ‘as appearances they cannot exist in themselves but only in us. What objects are in themselves, apart from all the receptivity of our sensibility, remains completely unknown to us. We know nothing but our mode of perceiving them—a mode which is peculiar to us, and not necessarily shared in by every being.’
 What is it in us that begins to raise objections to this view of the relative reality of the visible world? We are firmly anchored to what the senses show us. Perceptible reality is the starting point of our thought. Sense-thinking characterizes the natural action of the mind, and we refer to sense as final proof.
 It is not necessary to think that appearances themselves are illusions, or that the senses show us an illusory world. They show us part of reality. Is not the starting point of illusion rather the taking of appearances for all ultimate reality and the belief that sense perception is the sole standard of the real? The seen world is real but does not embrace reality. It is built out of invisible realities which surround it on every side. The visible world is contained in a much greater invisible world (invisible to us) and we do not lose one by studying the other but enlarge one into the other. But as our natural everyday logic is so closely connected with sense-thinking it fights against this enlarging of the world, and its actual form of understanding becomes a psychological barrier to further understanding.
 If we could in some unknown way apprehend the totality of things apart from the senses we would, according to many early authorities, perceive the universe as the unity that its name originally implies.

[9 of 9] Meister Eckhart (1260-1328, Germany): primary subject "Knowledge (general)" (search under Inner Life/Mind, Psyche, Soul, Spirit)": detail "Quoted in "Mysticism", by Evelyn Underhill"
Every time that the powers of the soul come into contact with created things, they receive the ‘create’ images and likenesses from the created thing and absorb them. In this way arises the soul's knowledge of created things. Created things cannot come nearer to the soul than this, and the soul can only approach created things by the voluntary reception of images. And it is through the presence of the image that the soul approaches the created world: for the image is a Thing, which the soul creates with her own powers. Does the soul want to know the nature of a stone—a horse—a man? She forms an image.