In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Indeed, the flag-bearer of French Militant Secularism says that Islaam is a religion in crises, so we say to him, “The curse of Allaah is upon the liars – those who slander Allaah, slander the religion Allaah has ordained and slander Allaah’s final Messenger. Indeed, we have no doubt that the final religion ordained by Allaah is perfect and can never be overcome, and we seek Allaah’s protection against abandoning our religion and embracing your Kufr because this is what you desire”.
Imaam As-Sadi [rahimahullaah] said:
Indeed, it is impossible to rectify the souls and acquire virtue solely through the worldly sciences. Experience and clearly witnessed circumstances are the greatest proofs regarding this affair, because despite its advancement and vastness it has been unable to nurture and rectify the souls. What the Religion of Islaam propagates is that which is entrusted with this rectification – it is what will guide the thoughts towards the truthful and authentic sources of knowledge, and guide the actions of the people towards good and prevent them from evil. Islam is The Rectifier of the Creeds and Manners- the thing that cultivates the thoughts [upon righteousness], urges towards virtuousness and prevents from depravity. The essence of that which the religion calls to regarding belief in the Unseen, which includes belief in Allaah and that which He possesses of Names, Attributes and Actions of perfection; belief in Angels, belief in recompense for one’s good and bad deeds in this life and the next, which cannot be known except through the Messengers, is what acquaints a person with the fact that rectification – in reality – is not possible through other than sound belief and the religion of Islaam. Therefore, even if the worldly sciences rectify [some] affairs based upon that which people know in detail, it will still not be equal [in perfection, excellence etc] to the knowledge of the Messengers [in the least]. It will neither reach that which is reached through the knowledge of the Messengers nor can it influence the souls in the manner in which the knowledge of the Messengers has done; for indeed the souls do not voluntarily submit except through belief in Allaah, belief in His Angels, belief in His Books, belief in His Messengers and belief in the hereafter. And without this, voluntary submission is impossible, as is well known regarding human nature. [Ref A]
Imaam As-Sadi [rahimahullaah] said:
And what is well known is that Allaah neither loves ignorance nor doubts, neither confusion nor misguidance; rather He loves the religion, knowledge and certainty.
Indeed, Allaah [The Most High] dispraised confusion, saying:
قُلْ أَنَدْعُو مِن دُونِ اللَّهِ مَا لَا يَنفَعُنَا وَلَا يَضُرُّنَا وَنُرَدُّ عَلَىٰ أَعْقَابِنَا بَعْدَ إِذْ هَدَانَا اللَّهُ كَالَّذِي اسْتَهْوَتْهُ الشَّيَاطِينُ فِي الْأَرْضِ حَيْرَانَ لَهُ أَصْحَابٌ يَدْعُونَهُ إِلَى الْهُدَى ائْتِنَا ۗ قُلْ إِنَّ هُدَى اللَّهِ هُوَ الْهُدَىٰ ۖ
‘’Say (O Muhammad): “Shall we invoke others besides Allah (false deities), that can do us neither good nor harm, and shall we turn on our heels after Allah has guided us (to true Monotheism)? – like one whom the Shayaateen (devils) have made to go astray, confused (wandering) through the earth, his companions calling him to guidance (saying): ‘Come to us.’ “Say: “Verily, Allah’s Guidance is the only guidance.’’ [Soorah Al An’aam: Ayah: 71]
Indeed, we have been commanded to ask Allaah [The Most High] to guide us to the straight path and this necessitates knowledge of the truth and acting upon it, and the Qur’aan is the cure, guidance and light. The Muslims are agreed upon the fact that doubt and confusion are unpraiseworthy, and it is expected – absolutely- that a person who does not possess knowledge of something is obligated to keep quiet and seek knowledge via its (sound) sources. Those Mulhidoon – the most doubtful of doubters, who command the people to eradicate the truth from the hearts in order to direct the hearts to other than it – are opponents of the Book, the Sunnah and the consensus of those considered to be people of sound reasoning. They (i.e. the Mulhidoon) are followers of their misguided leaders. [Ref 1]
Imaam Ismaa’eel Bin Abdur-Rahmaan – known as As-Sadee (rahimahullaah) said:
The people of shirk said to the Muslims: ‘’follow our path and abandon the religion of Muhammad (sallal-laahu-alayhi-wasallam)’’, so Allaah revealed the ayah: ‘’Say (O Muhammad): Shall we invoke others besides Allah (false deities), that can do us neither good nor harm, and shall we turn on our heels;’’ Meaning: (shall we turn into) disbelief ‘’after Allah has guided us (to true Monotheism)?’’, and so that we become like you? – those whom the devils have made to go astray in the earth.
And so that we become like you by disbelieving after believing, similar to a man who set out on a road with some people, but he got lost. So, the devils made him confused and he wandered in the earth, whilst his companions are on the (right) road. His companions started calling him saying: ‘’Come to us, we are on the (right) road”, but he refuses to go to them. This is similar to the one who follows the (people of shirk) after being acquainted with the (message of) Muhammad (sallal-laahu-alayhi-wasallam). And Muhammad (sallal-laahu-alayhi-wasallam) is the one calling to the (right) road and the road is Islaam. [Ref 2]
Allaah (The Most High) said:
وَقَالَ الَّذِينَ كَفَرُوا لِلَّذِينَ آمَنُوا اتَّبِعُوا سَبِيلَنَا وَلْنَحْمِلْ خَطَايَاكُمْ وَمَا هُم بِحَامِلِينَ مِنْ خَطَايَاهُم مِّن شَيْءٍ ۖ إِنَّهُمْ لَكَاذِبُونَ
And those who disbelieve say to those who believe: “Follow our way and we will verily bear your sins,” never will they bear anything of their sins. Surely, they are liars. [29:12]
Imaam Ibn Katheer (rahimahullaah) said:
Allaah (The Most High) informed (us) about the disbelievers of Quraish that they said to those amongst them who believed (in the message of Muhammad) and followed the (right) guidance: ‘’Abandon your religion, return to our religion and follow our way. We will verily bear your sins if you have any’’, just as a person says: Do this and your sin is upon my neck. So Allaah declared their statement false, saying that never will they (i.e. the Quraish) bear anything of their (i.e. the believers) sins. Surely, they are liars. That is because no one will bear anything of the sins of others. 
Imaam At-Tabari (rahimahullaah) said:
They (i.e. disbelievers of Quraish) said (to the believers): Be upon the likes of what we are upon, such as our denial of the resurrection after death and that there will be no good recompense and punishment for the deeds of the people. If you follow our way in these affairs and are raised up after death (i.e. we doubt it), and you are recompensed for your deeds, we will indeed bear the burden of your sins…
Imaam Ibnul Jawzi (rahimahullaah) said that Mujaahid (rahimahullaah) said:
This is the statement of the disbelievers of Quraish to those believers amongst the people of Makkah; they said to them: ‘’Neither we nor you will be resurrected, so follow us. If anything is brought against you (i.e. we doubt it), the burden will be on us.’’ Allaah said that they (i.e. disbelievers of Quraish) are liars due to the claim that they will bear the sins of the (believers). 
Imaam As-Sadi [rahimahullaah] said:
Allaah [The Most High] said:
[ لَقَدۡ مَنَّ ٱللَّهُ عَلَى ٱلۡمُؤۡمِنِينَ إِذۡ بَعَثَ فِيہِمۡ رَسُولاً۬ مِّنۡ أَنفُسِهِمۡ يَتۡلُواْ عَلَيۡہِمۡ ءَايَـٰتِهِۦ وَيُزَڪِّيہِمۡ وَيُعَلِّمُهُمُ ٱلۡكِتَـٰبَ وَٱلۡحِڪۡمَةَ وَإِن كَانُواْ مِن قَبۡلُ لَفِى ضَلَـٰلٍ۬ مُّبِينٍ – Indeed, Allah conferred a great favour on the believers when He sent among them a Messenger (Muhammad) from among themselves, reciting unto them His Verses (the Qur’an), and purifying them (from sins by their following him), and instructing them (in) the Book (the Qur’an) and Al-Hikmah [the wisdom and the Sunnah of the Prophet (i.e. his legal ways, statements, acts of worship, etc.)], while before that they had been in manifest error. [3:164]
Allaah [The Most High] said:[ وَٱذۡكُرُواْ نِعۡمَتَ ٱللَّهِ عَلَيۡكُمۡ إِذۡ كُنتُمۡ أَعۡدَآءً۬ فَأَلَّفَ بَيۡنَ قُلُوبِكُمۡ فَأَصۡبَحۡتُم بِنِعۡمَتِهِۦۤ إِخۡوَٲنً۬ا وَكُنتُمۡ عَلَىٰ شَفَا حُفۡرَةٍ۬ مِّنَ ٱلنَّارِ فَأَنقَذَكُم مِّنۡہَاۗ كَذَٲلِكَ يُبَيِّنُ ٱللَّهُ لَكُمۡ ءَايَـٰتِهِۦ لَعَلَّكُمۡ تَہۡتَدُونَ – And remember Allah’s Favour on you, for you were enemies one to another but He joined your hearts together, so that, by His Grace, you became brethren (in Islamic Faith), and you were on the brink of a pit of Fire, and He saved you from it. Thus, Allah makes His Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.,) clear to you, that you may be guided. [3:103]
Allaah [The Most High] said: [ ٱلۡيَوۡمَ أَكۡمَلۡتُ لَكُمۡ دِينَكُمۡ وَأَتۡمَمۡتُ عَلَيۡكُمۡ نِعۡمَتِى وَرَضِيتُ لَكُمُ ٱلۡإِسۡلَـٰمَ دِينً۬اۚ – This day, I have perfected your religion for you, completed My Favour upon you, and have chosen for you Islam as your religion]. [5:3]
Allaah [The Most High] said: [وَمَنۡ أَحۡسَنُ مِنَ ٱللَّهِ حُكۡمً۬ا لِّقَوۡمٍ۬ يُوقِنُونَ – And who is better in judgement than Allah for a people who have firm Faith]. [3:50] Whoever utilises sound intellect to examine what the Messengers brought [i.e. the revelation] – what they commanded and guided the people to, such as knowledge and Awareness of Allaah, the worship of Allaah alone, turning to Allaah in repentance and obedience with true Faith (Islamic Monotheism) and the command to fulfil all the rights [of the people] based on courteous good will, perfecting one’s actions [i.e. based on sincerity to Allaah alone] and treating others with kindness [by sincerely seeking to benefit them though one’s knowledge, wealth or position], and that which they [i.e. Messengers] forbade; then thereafter he examines what the Mul’hidoon call to, he will know that good [and its outcomes], success, sound rectification of the hearts and deeds, [sound rectification of] the worldly affairs and [sound rectification of the religious affairs and their end results in the afterlife] are all in agreement with what the Messengers called to.
On the other hand, he will know that the call of the Mul’hidoon is designed to do away with good manners [traits, characteristics etc], whose end result is nothing but complete chaos and a state in which one goes along with lust [or evil desires of the soul] until the animals become more noble and beneficial than humans. This is no doubt their state of affairs – clearly manifested by what they are upon and what they proclaim with their tongues. Among the most amazing of affairs is that many contemporary writers and politicians seek to remedy the many social ills and try to do so do from many angles, however as for the problem of Il’haad – whose surge has carried away the majority of young people – they have not rushed to stop it by returning to sound Eemaan and certainty; rather they [i.e. the Mul’hidoon] have been abandoned to wander blindly in their misguidance and wavering in beguilement, and thus the social ills they seek to remedy gives birth to other social ills- because if the path to remedying social ills is not based on Eemaan and sound Deen, they will increase and become worse. [End of quote] [Ref 6]
Meaning of the terms Il’haad, and Mul’hid [plural (Mul’hidoon)]: The Mul’hidoon are the people of Il-haad. Ilhaad means to turn away from that which one is obligated to believe in or do. This is a general definition of Il’haad and anyone who turns away from that which is obligated upon him to believe or do, then such a person is referred to as a Mul’hid. But Il’haad is of two types: Major Il’haad and Minor Il-haad.
Complete Il’haad is to turn away from Islaam completely and that is Major Il’haad, which exits a person from the fold of Islaam, such as the Il’haad of the communists, the idol worshippers and those similar to them. Minor Il-haad does not exit a person from the Religion of Islaam, such as turning away from some actions. Allaah [The Most High] said: [وَمَن يُرِدْ فِيهِ بِإِلْحَادٍ بِظُلْمٍ نُذِقْهُ مِنْ عَذَابٍ أَلِيمٍ -And whoever inclines to evil actions therein or to do wrong, him We shall cause to taste a painful torment.” [22:25] [Ref 7]
[Ref A]: Al-Adillatul Qawaati Wal-Baraaheem Fee Ibtaalil Usoolil Mulhideen. Page 48
 [Al-adillatul Qawaatiq Wal-baraaheen Fee Ibtaali Usoolil Mulhideen. Page 15. Abridged & slightly paraphrased]
 [Al-Misbaah Al-Muneer Fee Tahdheeb Tafseer Ibn Katheer. Page 428]
 Tafseer Ibn katheer
 Tafseer At-Tabari
 Zaadul Maseer
[Ref 6: An Excerpt from ‘Al-Adillatul Qawaatiq’ pages 40-41′. slightly paraphrased];