I should say at once that I am a heretic as to this explanation and that I shall expound to you another explanation based upon some work of my own, an explanation which seems to me to be more in accordance with our scientific ideas and with the whole body of facts which have to be explained.

We have to remember that a new theory must take account of the old well-attested facts of science just as much as of the very latest experimental results which have led to its production.
To put ourselves in the position to assimilate and to criticise any change in ultimate scientific conceptions we must begin at the beginning.

So you must bear with me if I commence by making some simple and obvious reflections.

Let us consider three statements, (i) 'Yesterday a man was run over on the Chelsea Embankment,' (ii) 'Cleopatra's Needle is on the Charing Cross Embankment,' and (iii) 'There are dark lines in the Solar Spectrum.' The first statement about the accident to the man is about what we may term an 'occurrence,' a 'happening,' or an 'event.' I will use the term 'event' because it is the shortest.

In order to specify an observed event, the place, the time, and character of the event are necessary.