“Indeed, once Kant had discovered the Humean problem of skepticism about the universality and necessity of first principles, he generalized it not only to the first principles of “speculative philosophy,” that is, theoretical cognition, but also to the first principle of practical philosophy, the fundamental principle of morality. Thus, from a methodological point of view, Kant’s project in philosophy became that of undermining both Humean and Pyrrhonian skepticism in both theoretical and practical philosophy, and, much more incidentally, along the way refuting Cartesian skepticism about external objects as a nagging but by no means central problem in theoretical philosophy.”

From Five Types of Ethical Theory (1930)

On Electro-magnetic forces (March 10, 1840), in Annals of Electricity, Vol. 4, p. 484.

Die Scheu vor der Spekulation, das angebliche Forteilen vom bloß Theoretischen zum Praktischen, bewirkt im Handeln notwendig die gleiche Flachheit wie im Wissen. Das Studium einer streng theoretischen Philosophie macht uns am unmittelbarsten mit Ideen vertraut, und nur Ideen geben dem Handeln Nachdruck und sittliche Bedeutung.
Vorlesungen über die Methode des akademischen Studiums ( Seventh Lecture http://www.zeno.org/Philosophie/M/Schelling,+Friedrich+Wilhelm+Joseph/Vorlesungen+%C3%BCber+die+Methode+des+akademischen+Studiums/7.+%C3%9Cber+einige+%C3%A4u%C3%9Fere+Gegens%C3%A4tze+der+Philosophie,+vornehmlich+den+der+positiven+Wissenschaften), Friedrich Wilhelm Joseph von Schellings sämmtliche Werke, V, 1859, p. 277 http://babel.hathitrust.org/cgi/pt?q1=%22nur%20Ideen%20geben%22;id=uva.x002624295;view=1up;seq=301;start=1;sz=10;page=search;num=277.
On University Studies (1803)

1940s, Philosophy for Laymen (1946)
Context: The demand for certainty is one which is natural to man, but is nevertheless an intellectual vice. If you take your children for a picnic on a doubtful day, they will demand a dogmatic answer as to whether it will be fine or wet, and be disappointed in you when you cannot be sure. The same sort of assurance is demanded, in later life, of those who undertake to lead populations into the Promised Land. “Liquidate the capitalists and the survivors will enjoy eternal bliss.” “Exterminate the Jews and everyone will be virtuous.” “Kill the Croats and let the Serbs reign.” “Kill the Serbs and let the Croats reign.” These are samples of the slogans that have won wide popular acceptance in our time. Even a modicum of philosophy would make it impossible to accept such bloodthirsty nonsense. But so long as men are not trained to withhold judgment in the absence of evidence, they will be led astray by cocksure prophets, and it is likely that their leaders will be either ignorant fanatics or dishonest charlatans. To endure uncertainty is difficult, but so are most of the other virtues. For the learning of every virtue there is an appropriate discipline, and for the learning of suspended judgment the best discipline is philosophy.
But if philosophy is to serve a positive purpose, it must not teach mere skepticism, for, while the dogmatist is harmful, the skeptic is useless. Dogmatism and skepticism are both, in a sense, absolute philosophies; one is certain of knowing, the other of not knowing. What philosophy should dissipate is certainty, whether of knowledge or of ignorance.

Source: Quantum Reality - Beyond The New Physics, Chapter 9, Four Quantum Realities, p. 159

Kantian Ethics (2008)

Alabama Republican Assemblies Luncheon, April 29, 2000. http://renewamerica.us/archives/speeches/00_04_29alral.htm.
2000

Source: Zen and the Art of Motorcycle Maintenance (1974), Ch. 29
Context: The Immortal Principle was first called water by Thales. Anaximenes called it air. The Pythagoreans called it number and were thus the first to see the Immortal Principle as something nonmaterial. Heraclitus called the Immortal Principle fire and introduced change as part of the Principle. He said the world exists as a conflict and tension of opposites. He said there is a One and there is a Many and the One is the universal law which is immanent in all things. Anaxagoras was the first to identify the One as nous, meaning "mind."
Parmenides made it clear for the first time that the Immortal Principle, the One, Truth, God, is separate from appearance and from opinion, and the importance of this separation and its effect upon subsequent history cannot be overstated. It's here that the classic mind, for the first time, took leave of its romantic origins and said, "The Good and the True are not necessarily the same," and goes its separate way. Anaxagoras and Parmenides had a listener named Socrates who carried their ideas into full fruition.

Source: Engineering cybernetics, (1954), p. vii