How we know what (and what not) reality is can only be properly answered by examining and understanding what knowledge is and how we know it. What is, (metaphysics), and how we know it, (epistemology), are the primary essentials on which a practical and reliable philosophy rests and this dependency makes these philosophy�s central issues. The importance of resolving these issues if found in the need to refute the claims of those who seek to enslave the minds of those unable to justify their beliefs, whether those beliefs are misguided or completely valid in spite of the inability to demonstrate its correspondence to reality.
I will not attempt to fully address these issues here since an adequate explanation that does justice to such an important question is for all intents and purposes beyond the scope of this thread. If you desire more information on this subject I suggest reading �Objectivism: The Philosophy of Ayn Rand� by Leonard Peikoff. Nevertheless this is an important subject and I will be following this thread and possibly adding to it.
On a more personal level, if it has life or death consequences it is real. Your ability to discriminate between life and what makes it worth living and the absolute finality of death (a precondition for fully appreciating the value of life) is directly proportional to your appreciation for and understanding of reality.
Without life, reality is irrelevant.
Sweet dreams.