Many read Quoholet (Ecclesiastes) and believe it to be written by a person full of despair and defeatism. I tend to disagree. In point of fact this is an essay written by a person that has spent a great deal of his life both living that life to its fullest measure and contemplating it, altogether.
After much experience of life and deliberation on that vast amount of wisdom gained, the man came to the realization that life, if lived in and for itself, had no real meaning. This is also reflected by us every day during the morning supplications of Shacharit:
“What are we? What is our life? What are our acts of kindness? What is our deliverance? What is our strength? What is our might? What can we say before You, Adonai, L-RD and Master of our fathers? Are not the mighty men as nothing before You? Famous men as though they had never been? The wise as if they were without knowledge? And men of understanding, as if they were devoid of intelligence? For most of their actions are a waste, and the days of their life are trivial in Your presence. The superiority of man over the beast is nothing for all is futile.”
This is not a defeatist attitude but one of quiet, reflective realism. This man is not lamenting the fact, but simply stating it.
The greatest question of all, "Is there, or is there not, a G-d?" is noticeably missing from all his equations. Why? Because he understood that this is one question with no pithy finite answer and therefore, one not befitting the main thesis of his present dissertation.
Like any great thinker, he does not intend to prove or disprove G-d, but assumes G-d, based upon all the evidence, both measurable and circumstantial present before him. That is really all that man is truly capable of on this present level of enlightenment. However it begs the question of faith. Is the assumption of G-d the same as faith in G-d? I believe the writer answers that inquiry with a resounding NO! Faith, by its hidden agenda, does require (even demands) some form of proof, albeit, ever so slim; whereas assumption requires only an observable and rational acceptance of life as life and for life's sake in all its myriad manifestations.
The author's final summation is one that any reasonable person must come to by assumption after living and contemplating, in true honesty, their own life:
"The sum of the matter, when all has been considered: Be in awe of G-d and keep His commandments, for this is mankind’s whole duty.” - Ecclesiastes. 12:13
For this writer those commandments happen to be the Torah of Moshe Rabbenu, given by HaShem on Mount Sinai. However, regardless of your particular bent the same truth applies: After all is said and done one must be true to their assumed idea of G-d or they are living a useless life of vanity and futility.