Is it blasphemy to be skeptical?

Skepticism about the hereafter is not only favored by the Quran it is actually required.

Consider how the word skepticism was used in the Quran. The word skepticism also means certainty. It is not only the same entomology, it is the same exact word. Why is that when they are complete opposites?

It is as if skepticism was used as a precursor to certainty.

"الَّذِينَ يَظُنُّونَ أَنَّهُمْ مُلاقُو رَبِّهِمْ وَأَنَّهُمْ إِلَيْهِ رَاجِعُونَ" (البقرة: 46)
"قَالَ الَّذِينَ يَظُنُّونَ أَنَّهُمْ مُلاقُو اللَّهِ كَمْ مِنْ فِئَةٍ قَلِيلَةٍ غَلَبَتْ فِئَةً كَثِيرَةً بِإِذْنِ اللَّهِ وَاللَّهُ مَعَ الصَّابِرِينَ" (البقرة: 249)
"وَقَالُوا مَا هِيَ إِلا حَيَاتُنَا الدُّنْيَا نَمُوتُ وَنَحْيَا وَمَا يُهْلِكُنَا إِلا الدَّهْرُ وَمَا لَهُمْ بِذَلِكَ مِنْ عِلْمٍ إِنْ هُمْ إِلا يَظُنُّونَ" (الجاثية: 24)
"وَمَا لَهُمْ بِهِ مِنْ عِلْمٍ إِنْ يَتَّبِعُونَ إِلا الظَّنَّ وَإِنَّ الظَّنَّ لا يُغْنِي مِنَ الْحَقِّ شَيْئًا" (النجم: 28 )
"وَمَا يَتَّبِعُ أَكْثَرُهُمْ إِلا ظَنًّا إِنَّ الظَّنَّ لا يُغْنِي مِنَ الْحَقِّ شَيْئًا" (يونس: 36)