To answer the question "what is the meaning of life" I will first frame my interpretation of such a question. The meaning of life as I see it is to confront Being itself. To do this one must refuse the anesthetizing irrelevancies of everyday existence and instead choose to live one's life oriented around nothing less than the most fundamental question: why are we here and what is our reason for being? The argument I will make from Heidegger, Plato, and Aristotle is that the "examined life" is the only life worth living. Our mission is to overcome the mechanistic, trivial, inauthentic mode of existence and look within. Certainly we must confront our finitude and understand that we are temporal beings, but I believe there is a limitation to a purely Heideggerian model of temporal realization that stops short of contemplating or striving towards the infinite, a limitation I take up below. I argue that the value of life comes from the pursuit and contemplation of the eternal, the ideal, a striving towards the highest good. My characterization of meaning in life is as such: you must strive towards the eternal and infinite, pursue the Platonic ideals of what is good, beautiful, peaceful, just, creative, and virtuous; however, the aspiration of pursuing such things is fruitless if not grounded in temporality. We must confront our finite existence (it would be foolish to think we are immortal and deserving to be among gods), and leverage that finitude as direction and motivation to actualize things in the world, for there will be a time where we are no more. Consider life as a two-dimensional vector: the magnitude is existentially acknowledging your finitude, and the direction is an actionable striving towards the highest goods. Each alone is an insufficient scalar. In the absence of a transcendent goal to pursue (the "forms", eternal truths, the "highest practicable goods"), your temporal endeavors will fall short of meaning. Yet without understanding the scarcity of life, trying to transcend is equally misguided. I explore a synthetic approach to reconcile Platonic and Aristotelian thought with the urgency of Heidegger and proclaim that confronting temporality and pursuing eternality is not a false dichotomy. The meaning of life is greatly contingent on one's ability to simultaneously manage their finitude (understanding that yes, we will die) whilst striving and pursuing the seemingly infinite, idealistic form, as perhaps in some sense, our temporal contribution can and will amount to something beyond us.
To support this we can start with Heidegger's concept of the true authentic mode of existence, otherwise known as Dasein. It is a call to live "authentically", in rejection of the "Das Man," the anonymous, conformist they-self that pushes the individual into low-minded trivialities and ultimately detracts from the honest, authentic mode of being. Per Heidegger, modernity is lost; we are lying to ourselves. Life is teeming with distraction, conformity, and clinging to convention without deeper questioning. We are alienated from confronting what matters most in our lives: Being. This is an exceptional diagnosis, as true now as it was then. Post-modern life's distractions in social media and careerism pull us away from exploring what matters. It is increasingly difficult to confront the essential facts of life. Most people live inauthentically. Heidegger posits that the pursuit of Dasein begins with the recognition of "Thrownness": we are plunged into a life we did not choose. We are cast into a world full of people, objects, questions, and inevitable mortality, and are forced to make sense of it. I think Heidegger's diagnosis of human shortcomings, and his imperative to turn and confront the essential truths of existence, is remarkably salient in getting us to explore the great question. However, where I part with Heidegger is in his orientation toward death as the terminus of meaning. Yes, death makes life meaningful; we are in effect plunged into a life towards a certain death. But I reject the notion that looking outside our mortal world constitutes escapism. I think Aristotelian thinking is necessary to fully satisfy the question of the meaning of life.
Humans, in recognition of their death, must have a direction towards which they are striving. I find the existentialist conclusions Camus and Sartre draw from broadly similar premises ultimately unsatisfying. The idea that the point of life is simply to be, and that essence is revealed only post-mortem or reflectively, strikes me as a passive undertaking of a scarce existence. This is why Plato and Aristotle provide direction for me. I think life is a pursuit towards the highest practicable good. We should strive to transcend, to imitate the forms, to be like the gods. Not as a means to cope with our temporality, but for the precise opposite: to use our finite time to become infinite. Do not live as if you will die tomorrow; live as if you will never die. Plato's highest practicable goods are ideals to aspire toward. Humans must pursue beauty and goodness because they are incomplete without it. To borrow again from Heidegger, I believe that Das Man emerges from the failure to strive for the highest achievable good on earth. This is the path to true human flourishing, and anything short of it will leave us in the leaky jar: the pleasure trap, always dissatisfied with our existence and seeking hedonistic ends in perpetuity. Aristotle employs Telos (purpose defined by function). I think our function is our actions and inquisitions towards the highest practicable good on Earth, the striving of it at least. Perhaps this does not materialize in the Platonic ideal of collective self-actualization where everyone philosophizes all day and brings into the world a post-suffering utopia. But I don't think it is a bad direction for your life's vector. Maybe in your life you undershoot that form and land a couple notches down: you cure a seemingly incurable disease, create beautiful art that inspires a generation, start a civil movement that brings about meaningful change, or make some marginal improvement in humanity that is directed, that follows the trails of the path that is the eternal, highest good.
This is what I mean by the vector. The magnitude, your confrontation with finitude, gives life its urgency. The direction, your aspiration toward the infinite and the good, gives it meaning. Each alone is insufficient: the person who acknowledges death but aims at nothing merely endures, and the idealist who strives toward the eternal without understanding the scarcity of their time is misguided. The examined life, as Socrates insisted, is the only life worth living, not because examination promises answers, but because it orients you. It aligns your finite existence toward something that may outlast it.