I see some people say that life/existence is meaningless. However, I assign existence with meaning, therefore it's NOT meaningless. Yes?
'Meaning of life' questions are exceptionally difficult, at any rate I find them so. I'm inclined to say that life is not meaningless merely because (or if) you believe it to have meaning. If, for instance, you believe that your life has meaning by virtue of your relation to a supernatural realm or being, then if there is no such realm or being it does not follow that your life is not meaningless; it follows only that you have a false belief that it has meaning.
One point to add is that 'life' in 'the meaning of life' does not or need not extend across every event or episode of which one's life consists. A life could have meaning overall even if segments or portions of it were neutral.
But let's start snipping with the scissors of analysis.
If there is a God then I accept that fulfilling God's purposes for us would constitute life's meaning. Someone might say, critiquing this: a meaningful life is an autonomous, self-chosen life but a God who has a purpose only in the pursuit of which our lives have meaning reduces, indeed removes, our autonomy. Two possible replies: (a) there is merely an assumption here that a meaningful life is an autonomous, self-chosen life, why should we accept it?; and (b) if God has purposes for us, we may still exercise autonomy in complying with those purposes or in rejecting them.
I still believe: if there is no supernatural realm or being of which the purposes could give meaning to our lives, then the mere belief that there is, does not save life from meaninglessness. How could it?
I naturally offer no view here about the existence or otherwise of the supernatural.
This heading covers so much. I'll narrow it, though of course others needn't, to the idea that a life has meaning if one injects meaning into it. This could be read as vacuously circular but I really only intend the following: the meaning of life is not externally defined (as on the supernatural model) or intrinsic to our natures (as in teleological views of human nature). Yet a life in which we make choices that satisfy us, fulfil inclinations with which we identify, or engage in activities which absorb our unforced attention, could reasonably be said to be a meaningful life.
In this case and on these naturalist assumptions, believing that our life is meaningful probably does entail that it is not meaningless. If meaning is created, is it possible for us to be mistaken about what we have created or failed to create?
I take no sides in this discussion between the standpoints of supernaturalism and naturalism.
I'd say it depends on what you mean by "(I think) life has meaning." Consider:
I pick up a signal from outer space. I think it has meaning, i.e., I think some intelligent entity produced it in an attempt to communicate. However, in reality, the signal is produced by an unintelligent physical phenomenon (say, a star going supernova). So, the signal does not actually have meaning (in the intended sense) in spite of me thinking so. I am simply wrong.
Of course, the signal might have meaning in a different sense: if I have no opinion about where this signal comes from or whether it is intended to communicate, but just find it beautiful and I hold that listening to it, in and of itself, gives meaning to my life, it seems I cannot be wrong about that, for this different sense of "meaning."
So I think it is with life -- in some sense of "meaning," you assigning it to life is enough for it to have it. In another sense, where "meaning" perhaps means that life serves some grander purpose outside what we can observe, just thinking that life has it is not enough for that to be the case.