Das Bedenkliche bei der Sache ist auch bloß die doch einzuräumende Möglichkeit, daß die letzte dem Menschen erreichbare Einsicht in die Natur der Dinge, in sein eigenes Wesen und das der Welt nicht gerade zusammenträfe mit den Lehren, welche theils dem ehemaligen Völkchen der Juden eröffnet worden, theils vor 1800 Jahren in Jerusalem aufgetreten sind.
Sämtliche Werke, Bd. 5, p. 154, E. Payne, trans. (1974) Vol. 1, p. 142
Parerga and Paralipomena (1851), On Philosophy in the Universities

“Childish and altogether ludicrous is what you yourself are and all philosophers; and if a grown-up man like me spends fifteen minutes with fools of this kind, it is merely a way of passing the time. I've now got more important things to do. Goodbye!”

Arthur Schopenhauer book Aphorisms on the Wisdom of Life

"Thrasymachus", in "On the Indestructibility of our Essential Being by Death, in Essays and Aphorisms (1970) as translated by R. J. Hollingdale, p. 76
Parerga and Paralipomena (1851), Aphorisms on the Wisdom of Life

“The view of things [called Pantheism] … — that all plurality is only apparent, that in the endless series of individuals, passing simultaneously and successively into and out of life, generation after generation, age after age, there is but one and the same entity really existing, which is present and identical in all alike; — this theory … may be carried back to the remotest antiquity. It is the alpha and omega of the oldest book in the world, the sacred Vedas, whose dogmatic part, or rather esoteric teaching, is found in the Upanishads. There, in almost every page this profound doctrine lies enshrined; with tireless repetition, in countless adaptations, by many varied parables and similes it is expounded and inculcated. That such was, moreover, the fount whence Pythagoras drew his wisdom, cannot be doubted … That it formed practically the central point in the whole philosophy of the Eleatic School, is likewise a familiar fact. Later on, the New Platonists were steeped in the same … In the ninth century we find it unexpectedly appearing in Europe. It kindles the spirit of no less a divine than Johannes Scotus Erigena, who endeavours to clothe it with the forms and terminology of the Christian religion. Among the Mohammedans we detect it again in the rapt mysticism of the Sufi. In the West Giordano Bruno cannot resist the impulse to utter it aloud; but his reward is a death of shame and torture. And at the same time we find the Christian Mystics losing themselves in it, against their own will and intention, whenever and wherever we read of them! Spinoza's name is identified with it.”

Arthur Schopenhauer book On the Basis of Morality

Part IV, Ch. 2, pp. 269 https://archive.org/stream/basisofmorality00schoiala#page/269/mode/2up-272 <br class="br">On the Basis of Morality (1840)

“Others … are in the habit of teaching that religion and philosophy are really the same thing. Such a statement, however, appears to be true only in the sense in which Francis I is supposed to have said in a very conciliatory tone with reference to Charles V: ‘what my brother Charles wants is also what I want’, namely Milan. Others again do not stand on such ceremony, but talk bluntly of a Christian philosophy, which is much the same as if we were to speak of a Christian arithmetic, and this would be stretching a point. Moreover, epithets taken from such dogmas are obviously unbecoming of philosophy, for it is devoted to the attempt of the faculty of reason to solve by its own means and independently of all authority the problem of existence.”

Arthur Schopenhauer book Parerga and Paralipomena

Andere wieder, von diesen Wahrheitsforschern, schmelzen Philosophie und Religion zu einem Kentauren zusammen, den sie Religionsphilosophie nennen; Pflegen auch zu lehren, Religion und Philosophie seien eigentlich das Selbe;—welcher Sah jedoch nur in dem Sinne wahr zu seyn scheint, in welchem Franz I., in Beziehung auf Karl V., sehr versöhnlich gesagt haben soll: „was mein Bruder Karl will, das will ich auch,”—nämlich Mailand, Wieder andere machen nicht so viele Umstände, sondern reden geradezu von einer Christlichen Philosophie;—welches ungefähr so herauskommt, wie wenn man von einer Christlichen Arithmetik reden wollte, die fünf gerade seyn ließe. Dergleichen von Glaubenslehren entnommene Epitheta sind zudem der Philosophie offenbar unanständig, da sie sich für den Versuch der Vernunft giebt, aus eigenen Mitteln und unabhängig von aller Auktorität das Problem des Daseyns zu lösen.
Sämtliche Werke, Bd. 5, p. 155, E. Payne, trans. (1974) Vol. 1, pp. 142-143
Parerga and Paralipomena (1851), On Philosophy in the Universities

“In general admittedly the Wise of all times have always said the same thing, and the fools, that is to say the vast majority of all times, have always done the same thing, i. e. the opposite; and so it will remain in the future.”

Arthur Schopenhauer book Aphorisms on the Wisdom of Life

Im allgemeinen freilich haben die Weisen aller Zeiten immer dasselbe gesagt, und die Toren, d.h. die unermessliche Majorität aller Zeiten, haben immer dasselbe, nämlich das Gegenteil getan; und so wird es denn auch ferner bleiben.
Parerga and Paralipomena (1851), Aphorisms on the Wisdom of Life

“The method of viewing things which proceeds in accordance with the principle of sufficient reason is the rational method, and it alone is valid and of use in practical life and in science. The method which looks away from the content of this principle is the method of genius, which is only valid and of use in art.”

Arthur Schopenhauer book The World as Will and Representation

Die dem Satz vom Grunde nachgehende ist die vernünftige Betrachtungsart, welche im praktischen Leben, wie in der Wissenschaft, allein gilt und hilft: die vom Inhalt jenes Satzes wegsehende ist die geniale Betrachtungsart, welche in der Kunst allein gilt und hilft.
Die Welt als Wille und Vorstellung, Zweiter Band, Ergänzungen zum dritten Buch, para. 36 (1859)
The World as Will and Representation (1819; 1844; 1859)

“In youth it is the outward aspect of things that most engages us; while in age, thought or reflection is the predominating quality of the mind. Hence, youth is the time for poetry, and age is more inclined to philosophy. In practical affairs it is the same: a man shapes his resolutions in youth more by the impression that the outward world makes upon him; whereas, when he is old, it is thought that determines his actions.”

Arthur Schopenhauer book Parerga and Paralipomena

Parerga and Paralipomena (1851), Counsels and Maxims

“Mostly it is the loss which teaches us about the worth of things.”

Arthur Schopenhauer