If nothing is selected, everything is selected ...

 From:  Michael Gibson
3171.2 In reply to 3171.1 
Hi PaQ, MoI does try to have some support for what is called "post pick" - that's where you pick objects to act on after launching a command instead of before launching a command.

Some older CAD programs can tend to be based on that kind of selection method.

So for example with Join, if you do not have anything selected when you run Join, it will prompt you and say "Select objects to join", and you can now go select some objects while you are actually still inside the join command - that's post pick.

If nothing being selected was taken as an alias for all selected, that would basically eliminate any possible post picking of individual objects...

Also I can imagine some potentially bad side effects of implicitly selecting all, for example with delete. One scenario that can be used with delete is to select an object which you are not sure if it is the only object around or not, but just to make sure you do an Invert selection and then a delete. If nothing is selected after the invert, then delete will not do anything so that removes other objects if they are present, but doesn't do anything if nothing else was around. If delete implicitly deleted everything when there was no selection, then that pattern would not work anymore... So it seems like there would be some potential for problems with that.

- Michael