Someone may say: "It is true that Islam had opposed all the human concerns which had existed at the time of the Qur'an's descent, and for that reason was able to lead the society of that day to true happiness and all the ideals of life. But the passage of time has changed the ways of life, and the cultural, scientific and industrial life of modern civilisation has no similarity with the simple life of fourteen centuries ago which was satisfied with elementary natural means.
Man has attained such a degree of progress and evolution as a result of his long and hard efforts, that if it is compared with the conditions of several centuries ago, it seems like comparing two totally opposite types.
How can the laws made tor arranging the life of that time, be adequate for managing the extensive and complex life of today? How can one of these two modes of life carry the burden of the other one on its shoulder?
The answer to this is: If the two eras appear to be different, it doesn't mean that they are different in the general aspects of life, but rather that the difference belongs to particular cases. In other words, in life a man needs food, clothes, a home to live in, means and equipment of transportation, a society to live in, sexual relations, commercial, technical and practical relations and such like as necessities of living.
These are unalterable general needs which man requires as a human being and as long as he has this nature and structure and this human life. Early men were not different from modern ones in this respect at all.
The difference is only the means by which his needs are met, as well as the needs of which he gradually becomes aware and learns how to secure the means of meeting them. To explain this point, early men fed in a simple manner on fruits, herbs and preyed meats he could find, but today they prepare thousands of different dishes and beverages, by their ingenuity and creative minds, each having various properties used by them, and various colours and touch, and many other peculiarities which cannot be enumerated.
In spite of all the differences between the two ways of living with respect to food, there is no difference between them in this, that all are food stuffs by which man satisfies his hunger and appetite. The same is true of clothing, dwelling etc.
You see that as these general beliefs have existed since the very first day of man's life in connection with the necessity of food, clothes, dwelling and other needs of life and have undergone no change in various periods, and if the first belief corresponds perfectly with the last progressive phase of belief, in the same way the general laws devised in Islam in accordance with nature's call and for the sake of securing happiness, are not annulled only because of the substitution of one means of living for another.
If the latest means are in harmony with the essence of nature, with no deviation from it, Islam agrees with them, but if they are contrary to the fundamental laws of creation, it disagrees whether they belong to the modern or ancient times.
Here are a number of incidental issues which belong to the events which take place at different times and change speedily, such as the decrees concerning wealth, rules for defense, facilitation of the means of communication, close contacts, regulations for managing a city etc., all of which are entrusted to one who is given the authority in an Islamic community or responsible for governmental affairs.
This Islamic authority or governor acts over big domain in the same way that a master of a house decides in managing his home and carries it out. The Islamic social authority has the right of decision in all the internal and external affairs of a Muslim community.
A Muslim authority has the right of taking any decision about war or peace, any financial and non-financial matters, and his decision must be in the interest of the society and after consultation with Muslims. God says:
These are about matters related to the people. These decrees and incidental decisions which must take place at all times and in all places will change with the change of means and interests, both of which are constantly changing, and sometimes they arise and sometimes disappear. These changeable decrees are different from general Divine decrees which include the Book and Traditions for which there is no annulment. Of course much may be said about this matter, but at the moment this will be sufficient.