You all seem to be arguing from the point of view of strict, chronological and absolute causality. Cause and effect on a quantum scale is not absolute, it is probabilistic in nature. And we conduct our day to day lives in a non-strict causality world. For example, many of us believe in a God who transcends time and space - divine technology not subject to strict causality. Many of us have had an experience involving prescience or prophecy come true - no strict causality there. Scientists often invoke "chance" when such prohpecies come true - but this is just making strict causality a probabilistic causality to explain something away. Back to strict causality when they want to explain away time travel though!

Hawking has put forth his "chronology protection conjecture" as a possible built-in structure in the universe to prevent destructive time paradoxes. That is not strict causality either. On a less serious note we often recognize such things as "Murphy's Law," "The Peter Principle," "gremlins," and such notions as destiny, karma and preordination.

The understanding of the true character of causality will have to wait until we have matter/spacetime interaction mechanisms in hand - then we will learn through experiment what cause and effect really are. In the meantime strict, chronological and absolute causality is no more than an opinion similar to "the world is flat." Let us not assume that it is a physical law - it is not - until we have experiments in hand to prove it.

• more at NIDS Forum - joseph - July 21, 2001 - 19:04 UTC