What does to have faith in the unseen, mean?
The Holy Quran demonstrates that the greatest quality that righteous people have is their having faith in the unseen. The scholars who interpret the verse, This is the (most honored, matchless) Book: there is no doubt about it (its Divine authorship and that it is a collection of pure truths throughout). A guidance for the God-revering, pious who keep their duty to God. Those who believe in the Unseen; establish the Prayer in conformity with its conditions, and out of what We have provided for them (of wealth, knowledge, power, etc.,) they spend (to provide sustenance for the needy and in Gods cause, purely for the good pleasure of God and without placing others under obligation.) (Al-Baqara Surah, 2:2-3), give two meanings to having faith in the unseen. First, They believe by resting on reasonable evidences although they have not seen anything. Secondly, they also believe while alone. That is, not only do they believe among Muslims but also while they are away from them.
The Unseen means two things: First are situations about which we know nothing but only Allah (SWT) knows, these have nothing to do with faith. Faith is in question not for this type of unseen, but for the unseen that the Quran announces and Prophet Muhammad (PBUH) makes explanations about.
For us, the unseen does not mean that what cannot be seen, but what is not seen. We believe in not the unseen without proofs but in reasonable unseen with sound proofs. (Elmalılı Hamdi Yazır)
The first to occur to the mind as far as having faith in the unseen is concerned is having faith in Allah (SWT) and other pillars pertaining to faith. This all has to do with the unseen.
The first step in belief is to affirm wholeheartedly. The beginning of this affirmation is understanding. The five senses let us understand, and understanding lets us believe. People, who do condemn themselves only into the boundaries of the five senses and do not go beyond, have not truly saved themselves from being animal like. To know through senses is the field of animals; and to understand, to grasp, and eventually to believe by making his senses serve reasoning is the field of human beings.
Animals are no different from human beings in looking at a fruit-tree. However, it is only human beings who can understand that a marvelous factory is working in that tree, that photosynthesis takes place in its trees that its fruits bear from the tree and even from the universe.
Hence, when it is said human being in absolute meaning, a believer should come to mind that has faith in the unseen.
These believers are not drowned with bounties and they know their Provider. They would not be stuck to works, but know the Creator Who has made them. As for those who do not believe in the unseen, they, like an insect which wander about the plates of the table, the segments of the factory, and the leaves of the books, cannot fully make use of this world and what is in, and waste away their lives.