The question "What is time?" has been an eternal problem for philosophers. However, you can define a physical time by making the second law of thermodynamics analytic. How can we define the time in our mind, then?
Can you say you are really happy so long as you feel happy? Or are there any requisites besides mere feelings?
It is evident that I have consciousness. How can I prove that there are other minds besides mine, then? If I cannot prove the existence of alter ego, must I accept solipsism?
You would think you have consciousness, but robots do not. What criteria should we apply for judging whether a certain system has consciousness or not? I would like to suggest a criterion: whether it can waver in its selection or not.