The traditional philosophy that alchemy, astrology and magic was built around in the west is Platonism and Hermeticism.
Now I think you meant to mention Hermeticism in your post, so let me say, be careful of works such as The Kybalion and The Emerald Tablets of Thoth (There is a traditional text called The Emerald Tablet, but there is a different modern text called The Emerald Tablets of Thoth) are NOT Hermetic. The Kybalion is part of the New Thought movement, and The Emerald Tablets of Thoth are similarly modern.
In the traditional Platonic and Hermetic world-view, there is a Material World, Spiritual World, and World of Soul. Spirit is an intermediary between the Soul and the Material World (This is explained further in Heinrich Cornelius Agrippa’s De Occulta Philosophy, or, Three Books of Occult Philosophy, a 16th Century text).
The Soul is superior to the Spirit, and the Spirit is superior to the Body, which we can read further about in Plato’s Timaeus, so with this Spirit is able to affect the material world and cause changes with it, and the Soul is able to direct spirit.
In Platonism, everything Proceedes from The One. Modern magicians commonly refer to The One as The All or The Source. The One is everything, or everything partakes of The One, everything descends from the purest part of The One down through a chain of being, being multiplied by the Soul of the World (The entire cosmos has its own Soul, Spirit, and Body, just as we do), and descending through the Heavenly Spheres, manifesting as all people, creatures, and plants, minerals, all events and everything else that is on the material world.
In this way, as Plotinus says in his Enneads, the Entire Cosmos is One Unified Living Being.
Everything in the material world descends from various Ideas in the Mind of The One (and this is so in Hermeticism as well, although I am not as well read on Hermeticism). This descends as previously mentioned by a Chain of Being. The stars and planets are the visible manifestation of this Chain of Being. All things are, but the Planets and Stars through traditional astrology reveal the cycles of this higher spiritual world very clearly, and allows for prediction through it with Horary, Natal, and Mundane astrology, and allows for the choosing of auspicious times through Electional Astrology. Electional Astrology is also part of astrological magick, as we choose a time when that Star whose influence we wish to call down is most strong and powerful.
In this way, the Material World certainly exists, but pure Spirit and the Soul is superior to it, and able to dominate it. This allows for the creation of the Philosopher’s stone in Alchemy, and the transmutation of Metals by altering the Spirit of an Object, which has been observed and written about much in traditional Alchemical texts.
Here is an Excerpt from Agrippa’s Three Books on Occult Philosophy regarding that:
“For as the powers of our soul are communicated to the members of the body by the spirit, so also the Vertue of the Soul of the World is diffused through all things by the quintessence: For there is nothing found in the whole world, that hath not a spark of the Vertue thereof. Yet it is more, nay most of all infused into those things which have received, or taken in most of this spirit: Now this spirit is received or taken in by the rayes of the Stars, so far forth as things render themselves conformable to them. By this spirit therefore every occult property is conveyed into Hearbs [herbs], Stones, Metals, and Animals, through the Sun, Moon, Planets, and through Stars higher then the Planets. Now this spirit may be more advantageous to us, if any one knew how to separate it from the Elements: or at least to use those things chiefly, which do most abound with this spirit. For these things, in which this spirit is less drowned in a body, and less checked by matter, do more powerfully, and perfectly act, and also more readily generate their like: for in it are all generative, & seminary Vertues. For which cause the Alchymists [alchemists] endeavour to separate this spirit from Gold, and Silver; which being rightly separated, and extracted, if thou shalt afterward project upon any matter of the same kind (i.e.) any Metall, presently will turn it into Gold, or Silver. And we know how to do that, and have seen it done: but we could make no more Gold, then the weight of that was, out of which we extracted the spirit. For seeing that is an extense form, and not intense, it cannot beyond its own bounds change and imperfect body into a perfect: which I deny not, but may be done by another way.”
(Three Books of Occult Philosophy, Book 1, Chapter XIV)