If your definition for existence is being able to see it with your eyes, then nothing can exist for a blind person. Sound does not exist. Odors do not exist. Infrared light does not exist. Heat does not exist.
It doesn't matter what your definition for existence is. It doesn't change the fact that the empty set is a useful idea.
Sense it how? Would you consider weak infrared light to exist? No human being could sense it with their senses alone, but they can build instruments that pick up the infrared light and depict its presence to a user via an interface compatible with their senses.
Name:
Anonymous2012-01-13 8:23
>>18 Would you consider weak infrared light to exist? No human being could sense it with their senses alone, but they can build instruments that pick up the infrared light and depict its presence to a user via an interface compatible with their senses.
Yes. It exists as long as you can detect using some device. For example, world in video game exists (even if in computer memory), in as sense, that you can detect it using video display.
Name:
Anonymous2012-01-13 8:26
>>11
my dick. i can't feel it, you can't feel it, but it's out there, somewhere
alright, but now, how do you know if the device is lying to you or not? Or perhaps your senses alone are lying to you. Optical illusions are an example of this. Once you realize the optical illusion, you see it for what it is. But what if you never realize it? How would you know that the illusion doesn't actually exist, even though you perceive it to legitimately exist from what you seen with your senses?
The point is that there are things that you can perceive that don't exist, and there are things that exist that you can't perceive. It might be better to use a different definition for existence, but I'm not going to try to offer one. Getting specific about it just opens doors for inconsistency.
# This codes demonstrates that empty_set exists
try:
empty_set = set()
except:
print 'there is no empty set!'
if empty_set.issubset(set((1,2,3,4))):
print 'empty set is subset of nonempty set'
else:
print 'empty set is not a subset'