strings: Let me put it in a different way. I met you yesterday. In the meantime you have changed. You have undergone a modification but I still have yesterday's picture of you. I meet you to-day with my picture of you and therefore I do not understand you—I understand only the picture of you which I acquired yesterday. If I want to understand you, who are modified, changed, I must remove, I must be free of the picture of yesterday. In other words to understand a challenge, which is always new, I must also meet it anew, there must be no residue of yesterday; so I must say adieu to yesterday.