Newton's third law of motion says that for every action there is an equal and opposite reaction. So how does that strong physical principle impact on philosophical questions like the creation of the universe (either by a prime mover like a god, or as some kind of QM fluctuation like the big bang). Where is the back-reaction there? In what sense did god's creation of the universe set up an equal and opposite action on him? Or for the big bang, where is its back-reaction? I ask the question mainly to highlight the standard confusion in people's thinking over causality - that there is a pusher and a pushee, so to speak. A cause and then an effect. Newton wrote the first two laws of motion in this spirit. He defined a local "prime mover", a force vector, first by the principle of inertia (so setting a zero baseline), then defining an acceleration (so the vector of action). But to complete the book-keeping of this scheme, he had to bring in the reaction - a mirror-image vector of action pushing right back. This is very weird and unrealistic. Until you step back and say Newton was just finding an economical way to deal up with the issue of global context, global constraints, in a mechanical description of the world. When you push to open a door, the equal and opposite action is not actually a mirror-image force vector that pops up on the part of the knob in contact with your hand. It is the whole atomic structure of the door, the frame to which it is attached, ultimately the earth to which it is anchored, that is the back-reaction. So it is in fact an asymmetry between a localised constructive push, and a global context of constraints, that explains why "a motion" occurs. Newton's genius was to make things much simpler than they really were (as he then did with gravity and "action at a distance"). The success of mechanics (triumphing over the scholastic aristotelan physics in the popular self-congratulatory mythology of science) has now become embedded as a psychological given in people's causal thinking. But my point is, even Newton's laws included the full story of local~global causality. It just hid it. And even then, anyone who asks mechanical questions about the creation of the universe - such as what was the first push, the first cause - still ought to complete the Newtonian analysis by looking seriously for the equal and opposite reaction that should be in there as part of the mechanics. Interestingly, I would argue that action~reaction must also be a part of any level of mechanics - so it should be present in quantum mechanics and relativistic mechanics. And this would be what the observer collapse issue is all about in QM. The context that pushes back to collapse the wavefunction. Or even more concretely these days, the transactional or absorber interpretations of QM which actually treat the back-reaction as a mirror-image retrocausal action. (Again, like Newton, a promising simplification, and again like Newton, an over-simplification from the philosophical point of view). What about relativity? Perhaps others can help out here. But my initial thought is that the way spacetime is related in relativity is exactly the kind of causal accounting trick I am talking about. Push the speed and you get a mirror image distortion in the time and mass measurements. A more complex model, but still the same basic trick of reducing a "real" local~global scale asymmetry to an "unreal" local~local action~reaction symmetry. To sum up, philosophical questions are usually posed as problems of mechanical causation (from freewill to creation debates). Yet the foundational model of mechanical causation - Newton's laws of motion - includes a third law that gets generally neglected. 1) What does this law really mean (it conceals the local~global scale story I say)? 2) And how must it affect answers to those standard big philosophical questions? 3) Or why would people be correct in disregarding it as they seem to?