Let us begin with what science, better still mathematics, can tell us for sure. Unfortunately, on deeper reflection, we find that science has nothing to say about the important things of life like love, justice, beauty, goodness, pity, joy, peace, death, or even about truth. As C. S. Lewis pointed out, science atomizes and destroys every worth-while thing that it looks at. A loved one becomes proteins and electric impulses. Music is just vibrations.
Responsibility vanishes into causes and effects.
Even our old favourites, proton, neutron, and electron, who seemed so solid, now disintegrate into worlds within worlds to infinite nothingness. Evidently science is therefore a useless starting-point for our purposes. That is why I shall begin with the Existentialists and say 'Here I am. Having started with meaning, we have only two options. Either I have a meaning, or I have not.