Time is just a concept, and cannot exist by itself.

As usual, your response packs quite a punch, Kleptin. "Indeed it is a necessary measurement, and your definition of "necessary" is accurate. However, the term "necessary" can apply to the existence of many things, not existence in general... I can argue that "time" as a concept is necessary for the development of human understanding of physical laws, but this does not automatically imply that time must exist in order for the universe to exist. Thus, whether or not the CONCEPT of time is necessary has nothing to do with whether TIME IN AND OF ITSELF exists." -I should have been clearer in my wording and meaning here. I was not saying that the concept of time is necessary regardless of the existence of actual time (although it is), but instead that it is actually "time in and of itself" that leads us to the concept of time. While playing around with syntax and trying to turn "necessary" against you, I believe I did not succeed in making the point I was trying to make. That is, that the existence of time is a necessary, as opposed to a contingent, truth - it is true of physical necessity that time exists, and would continue to exist independently of perception, in our observed spectrum of reality. This is related to your point that "In essence, when all motion or change stops, time effectively stops." The points in your paragraph preceding this sentence were all correct; it is the conclusion that is incorrect: If we follow the logic completely through, the conclusion would be that "In essence, when all motion or change stops, *existence* effectively stops, because there is nothing that exists that is not constantly in motion, and it is physically inconceivable that this should happen." If ALL motion did cease, life would automatically be blanked out instantly, but it is simply a fact that atomic and sub-atomic particles do not cease motion. So if the cessation of motion is ruled out by physical law, this argument becomes invalid (although theoretically very interesting.) In our universe, nothing cannot not be in constant motion and still "be" in any recognizable sense. "...[B]ut are these three dimensions actually three separate dimensions? Or is the separation of space in general into length, width, and depth purely due to flaws in our observation?" -Yes and no, respectively. Again, I will be arguing from the position of physical realism. While the names "dimension," "length," "width," and "depth" are obviously conventions of language, it seems self-evident that these ideas, in their most abstract form, derive from actual reality. Throw perception out the door completely: all objects that exist will still have orientation on three spatial axes (x, y, z) and one temporal (t). "Thus, our concepts of mass and space are on a different level from our concept of time. We draw the concepts of mass and space directly from our senses. Our concept of time must go through several assumptions first, namely, associating motion with change." -I have to disagree here and say that although we sense space and time differently, we still perceive them both directly - as I said, space is sensed externally and time is sensed internally (think of your inner monologue.) "Bacteria and other single celled organisms do not have free will. Their actions are monitored purely by chemical response. More importantly, bacteria and other single celled organisms cannot sense time and I attribute this to not being able to form opinions on how things should be and comparing it to how things are." -You got me here. I should have said, "I would also like to add that the passing of time is "felt" by all [intelligent] life, not humans exclusively." My mistake on that for certain. However, I would hasten to add that bacteria (and other single-celled organisms) also cannot really "sense" space, either, as they have no sense-organs, or any kind of organ for that matter. Just as they don't (and can't) know that they are in time, they don't know that they are in space. They do not sense space, but they do interact with space (and necessarily time) as you suggested. "Humans sense time in this way: First, they recognize mass and space inherently. They then begin to make assumptions and allow their bias to take over. They see a difference between a moving object and a stationary object, even though objectively, all things are moving. An infant seeing a mobile rotate in a stationary room would be able to form opinions on motion and change. Mobiles can stop moving, and when mommy pushes it, it moves again. The concept of time is derived from these human traits of combining these assumptions." -You say that humans recognize mass and space inherently and then use the example of an infant and a mobile. I argue that humans also recognize time inherently, as everything you described takes place on the four axes x, y, z, and t. To speak of one without the other is nonsense. "... [I]t makes a "sound" in the sense that a precise physical reaction has taken place." -Exactly. The reaction takes place with or without observers. I covered the rest earlier on. To end this round, I will say that indeed there *may be* nothing objectively supporting the existence of time *except physical necessity* and thus I conclude that time is not only real but also a fundamental component of reality itself.