I will examine first the distinction between testimony and observation. What is an observation? I observe something which is outside myself, and which I notice. I cannot help noticing it – I am forced to notice. At the same time, my observation does not change the thing I have observed. Moreover, the “I” who observes it is very impersonal: the same observation could have been made equally well by anyone in my place […] Now let us turn to testimony. It is never, and cannot ever be SOMEBODY who bears it. It is always and necessarily “I” – and if not I myself then somebody else who is another “I.” It is always an individual self, with his individual identity […] I can testify [in court] that John Smith was at the corner of Regent Street yesterday at 4 p.m., he was bare-headed, his expression was tired, etc. I said that I CAN testify – this means that “I am in a position to…” It can also mean that “I have the right.” And in certain situations I have to say that „I MUST bear witness.“

(Gabriel Marcel, Testimony and Existentialism, 1946)