What is Ijtihad, Qayas, and Ijma. What is the difference between them. When are they applied? Why Qayas is not accepted by legal experts?
Hussain Bin Sultan
For an explanation of Ijtihad, please refer to one of my earlier responses to a related question.
Qiyas (lit: drawing an analogy) is, in fact, a kind of Ijtehad. Qiyas implies trying to draw a directive for a situation, which is not expressly mentioned in the Shari`ah, from another situation, which closely resembles it and about which there is an express directive of the Shari`ah. For instance, 'if a person says that because the affects of taking drugs is comparable to that of consuming liquor, therefore, the punishment for taking drugs should be the same as consuming liquor', the person would be said to have made Qiyas (drawn analogy) on the punishment of taking liquor and derived the punishment for taking drugs.
Ijma` (lit: consensus) is used for something on which there is complete agreement of the Muslim scholars.
It would not be correct to say that that the legal experts do not accept Qiyas as a valid source of extracting laws, as most of them do. However, there are a few scholars (including Ibn Hazam) who do not consider Qiyas to be a valid source of extracting laws. For the reasons of Ibn Hazam's reluctance in accepting Qiyas as a valid source of deducing laws, please refer to his writings, some of which have also been translated into English.
October 5, 2001
 presuming that the person considers the punishment of taking liquor as one prescribed by the Shari`ah.
Answer published by Moiz Amjad