Although it has been said time and time again, it is necessary to repeat this truth, knowing that it will continue to be ignored by most: intuition comes first and is independent of its verbal expression. It must be said repeatedly because there are always examples of those who know, but cannot explain what they know; and not knowing how to explain it, or failing to explain it satisfactorily, does not mean they do not know. In truth, the problem often lies less in the explanation than in the listener. But it makes no difference: only perceives this he who, at least once in his life, has had a sudden understanding of something, an instant and reliable understanding that allowed him to judge and decide correctly, but whose foundations eluded rationalization. Those who have never experienced it, or have not noticed experiencing it, would do well to be aware of this possibility, so that they do not err by mistaking the ability to explain for knowledge.