“Those who have found this middle point are true and wonderworking adepts of science and reason. They are masters of the wealth of worlds, confidants and friends of the princes of heaven itself, and Nature obeys them because they will what is willed by the law which is the motive power of Nature. It is this which the Saviour of the world spoke of as the Kingdom of Heaven; this also is the Sanctum Regnum of the Holy Kabalah. It is the Crown and Ring of Solomon ; it is the Sceptre of Joseph which the stars obeyed in heaven and the harvests on earth.”

Source: Morals and Dogma of the Ancient and Accepted Scottish Rite of Freemasonry (1871), Ch. XXXII : Sublime Prince of the Royal Secret, p. 841

Introduction, Lesson I: Definition and Sphere of the Science.
Elementary Lessons on Logic (1870)

Canto XVI, lines 79–83 (tr. Sinclair).
The Divine Comedy (c. 1308–1321), Purgatorio

Source: The Best of All Possible Worlds (2006), Chapter 8, The End of Nature, p. 162.

The Advancement of Learning (1605)

Jan Patočka, cited in: Paul F.H. Lauxtermann, "Kant, Goethe, and the Mechanization of the World-Picture." in: Schopenhauer’s Broken World-View. Springer Netherlands, 2000. p.9

Science and the Unseen World (1929)
Context: If to-day you ask a physicist what he has finally made out the æther or the electron to be, the answer will not be a description in terms of billiard balls or fly-wheels or anything concrete; he will point instead to a number of symbols and a set of mathematical equations which they satisfy. What do the symbols stand for? The mysterious reply is given that physics is indifferent to that; it has no means of probing beneath the symbolism. To understand the phenomena of the physical world it is necessary to know the equations which the symbols obey but not the nature of that which is being symbolised.... this newer outlook has modified the challenge from the material to the spiritual world.<!--III, p.30

Introduction
A Treatise of Human Nature (1739-40)
Context: Nothing is more usual and more natural for those, who pretend to discover anything new to the world in philosophy and the sciences, than to insinuate the praises of their own systems, by decrying all those, which have been advanced before them. And indeed were they content with lamenting that ignorance, which we still lie under in the most important questions, that can come before the tribunal of human reason, there are few, who have an acquaintance with the sciences, that would not readily agree with them. 'Tis easy for one of judgment and learning, to perceive the weak foundation even of those systems, which have obtained the greatest credit, and have carried their pretensions highest to accurate and profound reasoning. Principles taken upon trust, consequences lamely deduced from them, want of coherence in the parts, and of evidence in the whole, these are every where to be met with in the systems of the most eminent philosophers, and seem to have drawn disgrace upon philosophy itself.