No rational argument will have a rational effect on a man who does not want to adopt a rational attitude.
Interpretation
Rational discussions fail with those unwilling to reason.
This quote by Karl Popper suggests that logical and rational arguments can only affect those who are open to reason. If a person is determined to reject rational thinking, no amount of logical persuasion will change their mind, highlighting the importance of openness in discussions and debates.
In practice
During a debate on controversial issues, you can use this quote to emphasize the importance of an open mind.
The growth of our knowledge is the result of a process closely resembling what Darwin called 'natural selection'; that is, the natural selection of hypotheses: our knowledge consists, at every moment, of those hypotheses which have shown their (comparative) fitness by surviving so far in their struggle for existence, a competitive struggle which eliminates those hypotheses which are unfit.
If you can't say it simply and clearly, keep quiet, and keep working on it till you can.
No particular theory may ever be regarded as absolutely certain.... No scientific theory is sacrosanct.
The belief in a political Utopia is especially dangerous. This is possibly connected with the fact that the search for a better world, like the investigation of our environment, is (if I am correct) one of the oldest and most important of all the instincts.
A rationalist is simply someone for whom it is more important to learn than to be proved right; someone who is willing to learn from others - not by simply taking over another's opinions, but by gladly allowing others to criticize his ideas and by gladly criticizing the ideas of others
Thus science must begin with myths, and with the criticism of myths; neither with the collection of observations, nor with the invention of experiments, but with the critical discussion of myths, and of magical techniques and practices.
The universe is a continuous web. Touch it at any point and the whole web quivers.
Habit is the denial of creativity and the negation of freedom; a self-imposed straitjacket of which the wearer is unaware.
Eloquence, at its highest pitch, leaves little room for reason or reflection, but addresses itself entirely to the desires and affections, captivating the willing hearers, and subduing their understanding.
All my possessions for a moment of time.
Humanity is not perfect in any fashion; no more in the case of evil than in that of good. The criminal has his virtues, just as the honest man has his weaknesses.
The incentive to peacemaking is love, but it degenerates into appeasement whenever justice is ignored. To forgive and to ask for forgiveness are both costly exercises. All authentic Christian peacemaking exhibits the love and justice-and so the pain-of the cross.
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