I had the privilege of collaborating with Dennis Sciama for a few years here in Trieste in building up the Astrophysical Sector of SISSA; and I am glad to tell him today that it has been for me an enjoyable and wonderful experience.

Now, first of all, I feel in some sense obliged to justify the subject of my contribution by saying that, at an age over eighty, it becomes much easier making some philosophical reflections about science than bringing some significant scientific consideration; that is why, in order to take part actively to this conference, intended to convey to Dennis all our wishes for further important scientific achievements, I have found myself confined to presenting only some epistemological puzzles. I was told by the organizers that this could be considered as tolerable; so that I have now only to ask for kindly forgiving me such a deviation from the main line of this meeting.

The second thing to do is to clarify what I mean in the title by “reality”. If scientists and philosophers are quite aware of the almost endless meanings that can be given to this word, at different levels of philosophical depth, this is not so for plain people, who generally stick to our immediate feeling that reality is what we perceive through our senses in our surroundings.