How we change what others think, feel, believe and do
Truth can be best discovered through reason and rational thought.
Although Greeks such as Pythagoras, Plato and Aristotle laid the foundations of logical thinking, freer thinking in the Western world about truth and falsehood was constrained for many centuries by the church in general and Catholics in particular. Galileo, for example, in the face of severe punishment had to recant his heresies about the movement of the earth.
Thomas Aquinas, in the 13th century, attempted to blend Greek Rationalism and Christian revelation. Although the church opposed scientific rationalism, they embraced the general idea within the bounds of religious teachings. The training of priests still includes the use of rational arguments to defend the teachings of the church.
Rationalists assume that the world is deterministic, and that cause and effect hold for all events. They also assume that these can be understood through sufficient understanding and thought. A priori (prior to experience) or rational insight is a source of much knowledge. Sense experience, on the other hand, is seen as being too confusing and tentative.
Logic and mathematics are classic rational disciplines, as is philosophy.
Rational argument is particularly attractive as it implies a superior intellect, and we all use it regularly, although the truth of our assertions is often open to question.
Variations on rationalism include:
Popper called his post-Positivist approach Critical Rationalism to signify his rejection of classical empiricism
Rationalism was particularly challenged by Positivism, which seeks empirical evidence rather than relying on the perceived unreliability of individual thinking.
René Descartes, Meditationes de Prima Philosophia (Meditations on First Philosophy),
Benedict de Spinoza, Ethics, (1862)
Gottfried Leibniz, Monadologie (Monadology and Other Philosophical Writings)
Immanuel Kant, Kritik der reinen Vernunft (Critique of Pure Reason), (1781)
Georg Hegel, Phänomenologie des Geistes (Phenomenology of Mind)