“The opinions that are held with passion are always those for which no good ground exists; indeed the passion is the measure of the holder's lack of rational conviction. Opinions in politics and religion are almost always held passionately.”

Speech to Working Men of Dundee July 14, 1875 - Speeches of Alexander Mackenzie during his recent visit...page 43

Source: The Collected Poems of W.B. Yeats

Letter to the Bailli de Ploën, as quoted in Recollections of the Private Life of General Lafayette (1835) by Jules Germain Cloquet, Vol. I, p. 24
Context: An irresistible passion that would induce me to believe in innate ideas, and the truth of prophecy, has decided my career. I have always loved liberty with the enthusiasm which actuates the religious man with the passion of a lover, and with the conviction of a geometrician. On leaving college, where nothing had displeased me more than a state of dependance, I viewed the greatness and the littleness of the court with contempt, the frivolities of society with pity, the minute pedantry of the army with disgust, and oppression of every sort with indignation. The attraction of the American revolution transported me suddenly to my place. I felt myself tranquil only when sailing between the continent whose powers I had braved, and that where, although our arrival and our ultimate success were problematical, I could, at the age of nineteen, take refuge in the alternative of conquering or perishing in the cause to which I had devoted myself.

The Raven and Other Poems (1845), Preface

Il y a dans le coeur humain une génération perpétuelle de passions, en sorte que la ruine de l'une est presque toujours l'établissement d'une autre.
Maxim 10.
Reflections; or Sentences and Moral Maxims (1665–1678)

Source: Life, the Truth, and Being Free (2010), p. 94

Source: In the Heart of the Heart of the Country and Other Stories

Source: An Unquiet Mind: A Memoir of Moods and Madness

Les passions sont les seuls orateurs qui persuadent toujours. Elles sont comme un art de la nature dont les règles sont infaillibles; et l'homme le plus simple qui a de la passion persuade mieux que le plus éloquent qui n'en a point.
Variant translation: The passions are the only orators who always persuade. They are like a natural art, of which the rules are unfailing; and the simplest man who has passion will be more persuasive than the most eloquent man who has none.
Maxim 8.
Reflections; or Sentences and Moral Maxims (1665–1678)