@████████- Personally, I prefer functionality similar to what you said in your reply rather than your original question... 

I don't believe it's possible to show/hide the Submit button via Field Rules, but it is possible via Javascript:

$('.Submit').show();
$('.Submit').hide();

Sometimes I want something even better than showing or hiding the button.  I make the button appear disabled/enabled.  Here's a simple way to do it that I like to use:

//enable instead of show
$('.Submit').prop('disabled', false);
$('.Submit').css('opacity', '1'); 

//disable instead of hide
$('.Submit').prop('disabled', true);
$('.Submit').css('opacity', '.4');

Here's a working example.  I made a collection with CSS Class of testCollection, and it has a single line field with CSS Class of testField.  And here's the full Javascript:

$(document).ready(function () {
  
  //when form is loaded, count the number of blank values in the fields with testField class
  //if there are no blank values, enable and show the Submit button.
  //if any values are blank, disable and fade out the Submit button.
  var blankFieldCount = 0;
  $('.testField input').each(function() { 
    if ($(this).val() == '') { 
      blankFieldCount = blankFieldCount + 1;
    }
  });
  if (blankFieldCount == 0) { 
    $('.Submit').prop('disabled', false);
    $('.Submit').css('opacity', '1'); 
  }
  else { 
    $('.Submit').prop('disabled', true);
    $('.Submit').css('opacity', '.4');
  }
  
  //when changes are made to any field in the testCollection, count the number of blank 
  //values in the fields with testField class
  //if there are no blank values, enable and show the Submit button.
  //if any values are blank, disable and fade out the Submit button.
  $('.testCollection').change(function(){
	var blankFieldCount = 0;
    $('.testField input').each(function() { 
      if ($(this).val() == '') { 
        blankFieldCount = blankFieldCount + 1;
      }
    });
    if (blankFieldCount == 0) { 
      $('.Submit').prop('disabled', false);
      $('.Submit').css('opacity', '1'); 
    }
    else { 
      $('.Submit').prop('disabled', true);
      $('.Submit').css('opacity', '.4');
    }
  });
  
});

Submit button is disabled on incomplete form:

And the Submit button is enabled when form is complete: