Of course, you won't answer it because you know that your claim that all human activity is physical in nature is entirely
false.
So, I'll answer for you because you will never grow a backbone.
Of course human beings can go back in time. We do this all the time mentally. We can do things with our minds that we cannot do physically.
Three of the definitions of "mental" are these:
of or relating to the mind (primary definition)
occurring or experienced in the mind.
And
of, relating to or being intellectual as contrasted with overt physical activity.
Likewise, in our minds we often conceive of effects prior to causes! Or to wax more Aristotleian -- with our minds, we can indeed cut to the chase and bypass material, formal and efficient causes (which we cannot do physically) and get right to Granddaddy of all Causes -- the Final Cause. For it is the Final Cause that speaks to a thing's purpose, its end to its goal -- indeed to its teleology.
With a little thought (which I certainly don't expect from you,since you have already denied the existence of mental activity!) we can think of many examples. A chess master can see the end from the beginning in his mind by seeing many moves ahead. He's mapped out his strategy and knows its end before ever touching a chess piece to implement the goal he has in his mind. The end game is entrenched in his mind without ever physically touching a chess piece.
This house I'm living in was chosen by my wife. I tasked her with the chore of choosing a house because she had a very specific kind of house in mind. She had a certain kind of kitchen in mind. A certain layout that would separate the master bedroom form the guest bedrooms. A certain kind of family room she wanted. A double-car garage, etc., etc. She had the house mapped out that would suit her purpose. The effect -- the finished product was in her mind, absent any causes! She wasn't thinking in terms of causes but only in terms of effects, a/k/a final causes.
People who design things often get ideas in their minds and the can see the end from the beginning. They can skip all the intermediate causes and jump immediately to the Final Cause and see that that their idea has a practical end -- a purpose.
When we encounter some kind of repair problem, we can often envision in our mind what's needed for a fix because we have the ability to see the end from the beginning. Only when we go to implement the fix physically are we bound to obey the Law of the Four causes in their order prior to reaching the final cause -- the purpose, the end -- the goal.
Just very recently, my handicapping partner in crime programmed a module in his program at my request. He asked that I lay out the design and beam it up to him. It was easy to do because even before I asked him to create the module, I knew the end from the beginning. I had the design, the end, the effect in my mind. I knew the chief end of the particular module and I was able to layout the design in a spreadsheet in short order. What took me a matter of mere seconds to do in my mind, and what took me several minutes to do in spreadsheet, it took my buddy 40 hours to physically accomplish my desired end.
I told you that my answer would be self-evident to all. Well...that is to say, to everyone who isn't simple-minded and acknowledges that human activity isn't just physical in nature.
