There are special terms which we use to explain particular meanings. It is necessary to understand these meanings, because they are related to our acts, and religious duties, such as the following words:
1. Al-Yaqin [certainty].
2. Ash-Shakk [doubt].
3. Az-Zann [most probable].
The Muslim Mukallaf is faced with the problem of learning the Shar'i precepts, or acquiring knowledge of the relevant subjects. In some cases, he may attain to certainty or conviction state (AlYaqin, in others he may attain to a most probable state of guessing called (Az-Zann), or be may stay in a state of doubt (Ash-Shakk). Henceforth, every one of these knowledge states has its own Shar'i [religious] precept specified in the Islamic Shari’ah. And now we are going to briefly explain these three terms:
Naturally, people's knowledge of things differ a great deal. Sometimes one obtains complete knowledge of something, without being mixed or having any doubt or uncertainty. Such as knowing that, this is wine, or that is usurped money, or this man is a just Imam of Jama’ah [the leader of a congregational Salat]. This is because one may positively know, or sense it, or because of having true evidence and testimonies proving the case. This is called the "Yaqin", (certainty).
So, "Yaqin is the full knowledge of something in the proportion of 100% without having any doubt or confusion".
Just as one becomes certain of something and obtains complete knowledge of it, one may sometimes doubt whether something is so or not.
For example, a state of mind in which one may doubt whether one had performed one's Salat correctly or not, after having finished it. Is this clothing Najis [ritually impure] or not? Is this blood, or something else? Shall one regard it Najis (as blood) or not? Is this thing usurped, so as to avoid it, or not?
In such cases man is perplexed, as he has no certain knowledge whether to be positive or the contrary, to decide this or that. This stare of mind is called Ash-Shakk or doubt. That is, his knowledge of it is 50%, and his ignorance of it is 50%, too.
As one can be in a state of certainty, or a state of doubt, one may also become in a most probable state of guessing called Az-Zann. Az-Zann is to prefer one aspect to another. For example, we may put a guess, at, a percentage or more than 50% that something has or has not happened.
There may appear signs which convince us that this particular money is usurped. This cannot be a case of certainty, yet it has a share of certainty higher than that of "doubt". This state is called Az-Zann. Consequently, man's knowledge is divided into three states or stages:
1. The state of Al-Yaqin (certainty).
2. The state of Ash-Shakk (Doubt).
3. The state of Az-Zann (most probable).