presentation must have a real causal connection with
| its object.  If a weathercock indicates the direction of the wind
| it is because the wind really turns it round.  If the portrait of
| a man of a past generation tells me how he looked it is because
| his appearance really determined the appearance of the picture
| by a train of causation, acting through the mind of the painter.
| If a prediction is trustworthy it is because those antecedents of
| which the predicted event is the necessary consequence 