I happen to be a believer in natural law. The idea of a law which is discoverable and not created by us but to which we ought to conform our civil or human laws. I think, in reading many of the responses and comments in this thread, that this may not be the majority view.

I would like to note that I am heavily influenced by the thought of John Duns Scotus, a medieval Franciscan philosopher and theologian. So, I take his understanding of natural law to heart here. He has a strict sense in which natural law can be applicable. Scotus, basically, states that a natural law must be a necessary law (perhaps necessary in the logical sense, where it would be true in every universe). As you can imagine, very little can be considered natural law by this definition. It would be dependent upon something which is present in every possible universe. And for Scotus, that would be God, the highest good and only necessary being.

Natural law in the strict sense then boils down to: love God and love neighbor. Everything else must be derived from this. The first half of the statement is necessary because we love what is good, our wills are ordered toward the good, and God as the highest good is that which we ought to love most. The second half of the statement boils down to a divine command theory.

Interestingly, Scotus notes that loving ones neighbor can be done with the same love that we love God. The reason being is that, in loving our neighbor, we really ought to will that they also love God, the highest good, and so the love of neighbor is a quasi-reflex love of God.

The reason I write all of this is because natural law in this sense is fairly simple. Everything else will either be divine command or our human law which we, hopefully, enact with an eye toward our natural law.

So, for Christians at least, the question goes all the way back to whether a law in some way can be said to honor love of God and love of neighbor.

I might add the idea of "exaggeration" to the mix of lies and truth. An exaggeration is an overstatement or amplification of what is true, and in this way might be said to be a lie.
Does the exaggeration of the truth make the truth more true? Does a lie, which does not completely obscure the truth but rather make it more than it really is, give us truth?

I am thinking of a book I read in high school, The Things They Carried by Tim O'Brien. The book is written as though from a Vietnam War veteran, but it turns out Mr O'Brien did not fight in the war and exaggerates much of it. Of course, the book is fictional. But the idea that what is said in the book is "truer than the truth" is an interesting thought.

Can something be a lie and yet "truer than the truth"? An exaggeration certainly seems to add something additional to the truth, which is not the truth, yet is intended to make some aspect clearer than it would otherwise be.

While I am not an expert in either mysticism or the Taoism, I would like to put a few thoughts forward. I have read the Tao Te Ching and must agree that:

No, completely not. As you shared with us, mysticism is another religious doctrine or way of living. Taoism is philosophy and self realisation. TTC is a tool where we can develop our knowledge and satisfaction in life without any kind of subterfuge. — javi2541997

I have found that the Tao Te Ching is something more akin to a philosophy which seeks to understand the deeper reality of the world and how we ought to behave in it. Perhaps something like metaethics? I say metaethics because it does not seem to me to present practical actions or particular actions but rather attitudes and such.

As for what mysticism is in itself? I like the first definition that was proposed.

[1] Belief that union with or absorption into the Deity or the absolute, or the spiritual apprehension of knowledge inaccessible to the intellect, may be attained through contemplation and self-surrender. — T Clark

My own experience of mysticism is founded in the Roman Catholic tradition. I am not claiming to be a mystic, but as a religious in the Catholic Church, I seek mystical union with God through prayer. But the goal is not knowledge per se but rather union with God in love.
The mystical tradition of the Catholic Church looks to find the heavenly reality of union with God in some aspect while still here on earth. It is a surrendering of the will in love to God in the hopes of a few moments of this mystical union. Knowledge and insight may follow, but that is a grace or gift which can be given but need not be. The experience may simply be that, an experience which is unlike any earthly experience, since what can be said of an experience of what transcends all earthly reality?

In this way, it is why I do not see Taoism as a form of mysticism.