It should be asked of those who deny the existence of the unseen: “Why do you reject its existence?”

They will answer [conjecturally]: “Such things cannot be quantified in the sensory realm or ascertained by experimentation”.

It should then be said in response: “If we were to hypothetically acquiesce that the unseen cannot be quantified in the manner you have alluded to, are the avenues towards establishment of the sciences not multifaceted? Most of these avenues do not fall into the realm of sensory perception anyways. Rather—even by your own admittance—your sensory abilities are woefully deficient as, by means of it, you only perceive some of earth’s processes, attributable causes and impetuses. However, you confess your inability to perceive all of them as evidenced by the work you carry out. For indeed you persist in the process of discovery and experimentation—sometimes confirming hypotheses, whilst rejecting (hypotheses) many other times.

Logically, if your circumstance is as described [i.e. limited in comprehension] as it relates to earth’s processes and the means by which they occur—which is widely perceived to varying degrees by all the Children of Ādam—how then can you completely negate the rest of existence including that of the heavens, the unseen, and the attributes of the Lord of Might and Greatness which is even greater than them both [i.e. the heavens and all that is unseen]. As you have not addressed such matters using your “scientific methods”. Thus, your outright negation of it is false by intellectual consensus. Rather, you are driven only by arrogance and pride.

If they then claim: “The heads and leaders of our scientific field have already addressed such matters and denied the existence of the unseen”.

We answer: “Indeed, the opinions and statements of your leaders contradict and oppose one another. They are unable to agree upon a collective statement, continuing to stumble over one another, confused, hypothesising new views that contradict previous ones, or agreeing with other previously discounted ones. Even if we were to hypothetically assume they have found agreement upon the complete negation of the unseen, how could one adopt the opinion of such people? For their truthfulness may not be ascertained. In fact, their deception, lies, and mistakes are well-known. Meanwhile, they suggest abandonment of the statements of all the Messengers—from the first to the last of them—whose truthfulness is ascertained with firmly established completely certain signs and portents. The sciences of the entire human race paling in comparison to their confirmed knowledge. None may reach true, sound knowledge or guidance except by means of them as agreed upon by the Messengers. For it is well-known that because of the books that have been revealed to the Messengers, their followers who are fully acquainted with the knowledge they have disseminated are fully able to challenge the ideology of any philosopher [including those who call themselves scientists]—from the first to the last of them. As all the Messengers, Prophets, their followers, along with sound intellectual reasoning and the innate, human disposition (unchanged by corrupted ideologies and creeds), are all in complete agreement upon having īmān in Allāh, His Books, His Messengers, and the Last Day, and every other obligatory aspect of the unseen. As for these godless heretics, they possess no narration or sound, correct intellect upon which they may base their views. Rather, they possess only lying, incorrect assumptions and opinions, contradictory hypotheses and theories, and blind following of other misguided, confused and lost individuals:

فَبِأَيِّ حَدِيثٍ بَعْدَ اللَّهِ وَآيَاتِهِ يُؤْمِنُونَ وَيْلٌ لِّكُلِّ أَفَّاكٍ أَثِيمٍ ‎﴿٧﴾‏ يَسْمَعُ آيَاتِ اللَّهِ تُتْلَىٰ عَلَيْهِ ثُمَّ يُصِرُّ مُسْتَكْبِرًا كَأَن لَّمْ يَسْمَعْهَا ۖ فَبَشِّرْهُ بِعَذَابٍ أَلِيمٍ

“Then in which speech after Allāh and His āyāt will they believe? Woe to every sinful liar, who hears the Verses of Allāh (being) recited to him, yet persists with pride as if he heard them not. So announce to him a painful torment!”
(Al-Jāthiyah, 45:6-7)

إِنَّ الَّذِينَ حَقَّتْ عَلَيْهِمْ كَلِمَتُ رَبِّكَ لَا يُؤْمِنُونَ ‎﴿٩٦﴾‏ وَلَوْ جَاءَتْهُمْ كُلُّ آيَةٍ حَتَّىٰ يَرَوُا الْعَذَابَ الْأَلِيمَ

“Truly! Those, against whom the Word (Wrath) of your Lord has been justified, will not believe. Even if every sign should come to them, – until they see the painful torment.”
(Yūnus, 10:95-6)