The following text is from Plato's Phaedo. The scene is Socrates' cell, in which he awaits his death, and the subject in this excerpt is how we attain Truth - absolute truth with no distortion of any kind. The yes man's name is Simmias and the main speaker is of course, Socrates. My comments are in the text and are coloured.
When does the soul attain truth?--for in attempting to consider
anything in company with the body she is obviously deceived.
Then must not true existence be revealed to her in thought, if at all?
And thought is best when the mind is gathered into herself and none of
these things trouble her--neither sounds nor sights nor pain nor any
pleasure,--when she takes leave of the body, and has as little as possible
to do with it, when she has no bodily sense or desire, but is aspiring
after true being?
And in this the philosopher dishonours the body; his soul runs away from
his body and desires to be alone and by herself?
That is true.
Socrates mistakes metaphysics for the divine just as an esthete might mistake work(s) of art for the artist that made them. ie. "Hemingway's thoughts are better revealed to us in his art that in a discussion with him."
Well, but there is another thing, Simmias: Is there or is there not an
Assuredly there is.
And an absolute beauty and absolute good?
But did you ever behold any of them with your eyes?
This is just what a nominalist would deny. It occurs to me that the role of doubting Thomas in the gospel could be called a chastisement of nominalism, because nominalism will get you into trouble in a hurry.
Or did you ever reach them with any other bodily sense?--and I speak not of
these alone, but of absolute greatness, and health, and strength, and of
the essence or true nature of everything. Has the reality of them ever
been perceived by you through the bodily organs? Or rather, is not the
nearest approach to the knowledge of their several natures made by him who
so orders his intellectual vision as to have the most exact conception of
the essence of each thing which he considers?
See? A strict nominalism will have trouble acknowledging the reality of things like justice, love, honour, duty... even the concept of truth itself. What we see mostly, however, that the average person will hold his own values to be obvious and will call only on those he disagrees with to provide him with the sort of proof that he himself lacks. Think of Richard Dawkins the whole effort to assert that evolution has been "proven" to be random because it happens to conform with one particular usage of Occam's Razor, which is itself a metaphysical construct and not a tangible entity.
And he attains to the purest knowledge of them who goes to each with the
mind alone, not introducing or intruding in the act of thought sight or any
other sense together with reason, but with the very light of the mind in
her own clearness searches into the very truth of each; he who has got rid,
as far as he can, of eyes and ears and, so to speak, of the whole body,
these being in his opinion distracting elements which when they infect the
soul hinder her from acquiring truth and knowledge--who, if not he, is
likely to attain the knowledge of true being?
What you say has a wonderful truth in it, Socrates, replied Simmias.
Socrates overlooks something that the ancient Jews either discovered or were told - Being has to be accounted for and not merely assumed. What sustains a soul, if it is indeed immortal, after it has been freed from the body? In a material account would it still not have a "body" or a "form" of some kind? Without that, how can it be said to be independent of anything else? If it has a form of some kind, then that is a limit to it's ability to know, and if it doesn't, it has been lost its identity in a kind of pantheistic existence. The God of the Jews is "I AM" and is the predicate of all that has ever existed and all that ever will exist. A soul that survives the death of the body is still dependent on God for its existence, just as the knowledge and wisdom it seeks is also. This unequal, dependent existence creates and reveals something very important: the Truth is not merely wisdom or knowledge, it is a relationship. God's existence keeps the soul from being consumed in a pantheistic universe. To know requires both someone to do the knowing and something that can be known and God sustains both by being the source of their independent existence.
There is also the small problem that without any kind of sense input, it is very hard indeed to see how anyone could come to understand any kind of metaphysics. How can anyone think about what the essence of a horse is if they have never seen a horse? C.S. Lewis once suggested that such an 'objective view' would not be omniscient, but blind.
And when real philosophers consider all these things, will they not be led to make a reflection which they will express in words something like the following? 'Have we not found,' they will say, 'a path of thought which seems to bring us and our argument to the conclusion, that while we are in the body, and while the soul is infected with the evils of the body, our desire will not be satisfied? and our desire is of the truth. For the body is a source of endless trouble to us by reason of the mere requirement of food; and is liable also to diseases which overtake and impede us in the search after true being: it fills us full of loves, and lusts, and fears, and fancies of all kinds, and endless foolery, and in fact, as men say, takes away from us the power of thinking at all... by reason of all these impediments we have no time to give to philosophy; and, last and worst of all, even if we are at leisure and betake ourselves to some speculation, the body is always breaking in upon us, causing turmoil and confusion in our enquiries, and so amazing us that we are prevented from seeing the truth. It has been proved to us by experience that if we would have pure knowledge of anything we must be quit of the body--the soul in herself must behold things in themselves: and then we shall attain the wisdom which we desire, and of which we say that we are lovers, not while we live, but after death; for if while in company with the body, the soul cannot have pure knowledge, one of two things follows--either knowledge is not to be attained at all, or, if at all, after death. For then, and not till then, the soul will be parted from the body and exist in herself
alone. In this present life, I reckon that we make the nearest approach to knowledge when we have the least possible intercourse or communion with the body, and are not surfeited with the bodily nature, but keep ourselves pure until the hour when God himself is pleased to release us. And thus having got rid of the foolishness of the body we shall be pure and hold converse
with the pure, and know of ourselves the clear light everywhere, which is no other than the light of truth.' For the impure are not permitted to approach the pure. These are the sort of words, Simmias, which the true lovers of knowledge cannot help saying to one another, and thinking.
I found this quoted exchange fascinating because Socrates does a nice job of suggesting the difficulties of nominalism but he appears to trip over the subject of Being (as almost all of the ancients did). I think that lead to a category error in regards what the nature of metaphysics is. It's not divine; it's a description of the true relationship between things. The thing that is the source of both the things and the relations - that is the divine.
It might be tempting to dismiss metaphysics as 'nonsense on stilts' as Jeremy Bentham famously did, because metaphysics is notoriously hard. In doing so I think we seriously undermine our relations with one another. We do have bodies and they do make the kind of knowledge Socrates and those of academic mind seek very hard to come by. Perhaps philosophic and scientific knowledge are not the highest goods (though they are goods). Perhaps the existence of the body suggests that the highest goods to be sought are those that deal with the proper relationship between unequal things. Rather than being seen as a prison, perhaps it is truer to say that it is a school or a hospital. The lowest low may not be ignorance after all, but Sin. Ignorance may be only a symptom of the real problem that we face. Rather than knowledge is power, perhaps suffering is knowledge is truer to real wisdom, and perhaps most of us would rather not seek or find that kind of wisdom. Such are the paradoxes of the Cross.