Does life have ultimate meaning? To answer this question we need to ask: what is the meaning of 'meaning'?
I define 'meaning' as: situatedness within a context. The reason we didn't get the meaning of a joke is that, as one sometimes says, "You had to be there." To understand a joke one must share the context in which the joke is situated. To understand the meaning of a foreign word one must be situated within the particular linguistic context.
Meaning is contextual. If there were no context, there would be no meaning.
So, does your life, my life, have ultimate meaning? Only if it has a place within a coherent context.
If there is no Creator God, there is no coherent, cosmic context. If no context, no meaning, because 'meaning' is situatedness within a context. Jean-Paul Sartre understood this, and believed that in a godless universe life has no meaning or purpose beyond the goals that each man sets for himself. In Being and Nothingness Sartre wrote: "Man can will nothing unless he has first understood that he must count no one but himself; that he is alone, abandoned on earth in the midst of his infinite responsibilities, without help, with no other aim than the one he sets himself, with no other destiny than the one he forges for himself on this earth." Which is to say: without God human life has no ultimate, cosmic meaning. Without God, there is no "grander scheme of things."
Commenting on Sartre, philosopher Leslie Stevenson writes: "There is no ultimate meaning or purpose inherent in human life; in this sense life is 'absurd'. We are 'forlorn', 'abandoned' in the world to look after ourselves completely. Sartre insists that the only foundation for values is human freedom, and that there can be no external or objective justification for the values anyone chooses to adopt." (Seven Theories of Human Nature)
Sartre is correct. Atheists who attempt to give life meaning are only spinning absurdities out of their own isolated existences. Only if a God who created the universe exists can our lives have meaning.