Rectification of Mankind and the Worldly Sciences–Imaam Sadi (rahimahullaah)
In The Name of Allaah, The Most Merciful The Bestower of Mercy
Indeed, it is absolutely impossible to rectify the souls and acquire virtuousness solely through the worldly sciences. Experience and clearly witnessed circumstances are the greatest proofs of that; because despite its advancement and vastness it has been absolutely unable to nurture and rectify the souls (upon excellent traits, manners, dealings, characteristics, creed) through which the rectification and success of mankind is dependent. Rather what the Religion of Islaam came with is that which is entrusted and commissioned with this rectification and sound upbringing. It is what is entrusted and commissioned with giving directions to the thoughts towards the truthful and authentic sources of knowledge; in directing the actions of the people towards good and preventing them from evil. Islam is The Rectifier for the creeds and manners. It is The Thing that cultivates the thoughts (upon goodness), urges towards virtuousness and prevents from depravity.
Therefore, the essence of that which the religion calls to of belief in the Unseen, in which enters 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; this acquaints a person with the fact that real rectification is not possible through other than sound belief and the religion of Islaam.
Therefore, even if the worldly sciences mend affairs based upon that which the people know in great detail, it will still not be equal to the sources of knowledge of the Messengers (in the least). It will neither reach that which is reached through the sources of knowledge of the Messengers nor can it affect the souls in the manner in which the sources of knowledge of the Messengers do. 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 of human nature.
[Abridged and slightly paraphrased…Source: Al-Adillatul Qawaatiq Wal Baraaheen Fee Ibtaalil Usoolil Mulhideen: page: 49-50]