سَنُرِيهِمْ ءَايَـٰتِنَا فِى ٱلْـَٔافَاقِ وَفِىٓ أَنفُسِهِمْ حَتَّىٰ يَتَبَيَّنَ لَهُمْ أَنَّهُ ٱلْحَقُّ ۗ أَوَلَمْ يَكْفِ بِرَبِّكَ أَنَّهُۥ عَلَىٰ كُلِّ شَىْءٍ شَهِيدٌ Qur’an Fussilat (41:53)Sanureehim a y a tin a fee al a f a qi wafee anfusihim h att a yatabayyana lahum annahu al h aqqu awalam yakfi birabbika annahu AAal a kulli shayin shaheed un
I.e., through a progressive deepening and widening of their insight into the wonders of the universe as well as through a deeper understanding of man's own psyche - all of which points to the existence of a conscious Creator.
Lit., "We will show them" or "make them see".
I.e., that He is almighty and all-seeing: a fundamental truth which, by itself, should be enough to remind man of his responsibility before Him.