<P> One solution to this problem takes a metaphysical view, in which the direction of time follows from an asymmetry of causation . We know more about the past because the elements of the past are causes for the effect that is our perception . We feel we can't affect the past and can affect the future because we can't affect the past and can affect the future . </P> <P> There are two main objections to this view . First is the problem of distinguishing the cause from the effect in a non-arbitrary way . The use of causation in constructing a temporal ordering could easily become circular . The second problem with this view is its explanatory power . While the causation account, if successful, may account for some time - asymmetric phenomena like perception and action, it does not account for many others . </P> <P> However, asymmetry of causation can be observed in a non-arbitrary way which is not metaphysical in the case of a human hand dropping a cup of water which smashes into fragments on a hard floor, spilling the liquid . In this order, the causes of the resultant pattern of cup fragments and water spill is easily attributable in terms of the trajectory of the cup, irregularities in its structure, angle of its impact on the floor, etc . However, applying the same event in reverse, it is difficult to explain why the various pieces of the cup should fly up into the human hand and reassemble precisely into the shape of a cup, or why the water should position itself entirely within the cup . The causes of the resultant structure and shape of the cup and the encapsulation of the water by the hand within the cup are not easily attributable, as neither hand nor floor can achieve such formations of the cup or water . This asymmetry is perceivable on account of two features: i) the relationship between the agent capacities of the human hand (i.e., what it is and is not capable of and what it is for) and non-animal agency (i.e., what floors are and are not capable of and what they are for) and ii) that the pieces of cup came to possess exactly the nature and number of those of a cup before assembling . In short, such asymmetry is attributable to the relationship between temporal direction on the one hand and the implications of form and functional capacity on the other . </P> <P> The application of these ideas of form and functional capacity only dictates temporal direction in relation to complex scenarios involving specific, non-metaphysical agency which is not merely dependent on human perception of time . However, this last observation in itself is not sufficient to invalidate the implications of the example for the progressive nature of time in general . </P>

Who had the idea that space and time are relative to the person measuring them