 Analogy is "qiyas" which means to use logic and reasoning to apply a known law to a new situation which is not originally covered in the law.  When a person does not know the specific law for a detailed item; analogy allows that person to use deduction in order to deduce a law from another law from a similar issue. In doing so, teachings of Ahadith are compared and contrasted with those of the Quran in order to make that injunction.

 In the Shia sect, there are four sources which jurists study in order to deduce laws. These sources are referred to as the "four proofs" which jurisprudence is based on. They are:  Quran  Sunnah  Consensus  Reasoning

 The Holy Book is the first sources for the laws in Islam. Since not all of the verses reveal laws and regulations; there must be more that we as Muslims must turn to in order to completely understand all aspects of life.

 The Sunnah refers to the actions, words, and assertions of the Holy Prophet and the Imams. This includes Ahadith and what people have witnessed the infallibles do; or what they have asked the infallibles and passed these messages on to the generations afterwards.

 This refers to the scholars having a unanimous view on a particular issue; leading to the proof that it was a view that has been received from the Holy Prophet. Nonetheless, in the Shia perspective, more research needs to be done in order to ensure that the consensus is backed by authenticity, as well as just and truthful scholars.

 This refers to having a clear rule for a certain issue--and if the rule is definite and absolute then it is binding and authentic.

 Amongst the Sunni sect, analogy or qiyas is the fourth proof--instead of reasoning. However, the view of the Shia scholars on this issue is that because the total of what has been received from the Prophet (pbuh) and the Imams is sufficient for our responsibility--the referral to analogy is strictly forbidden.

1.It is not necessary that every event and problem should have a specified rule-- since the problems to be solved are numerous and unlimited. Shia believe that general rules are applicable to all situations that are given within the Shari'ah. The only thing that is needed in order for a person to be able to derive such rules he must have competence, ijtihad, inquiry, and reflection.

2. Qiyas is based on conjecture, surmise, and superficial similarities--and it is based on matters which are not intelligible. As stated previously, one of the sources that the Shia use to deduce laws and jurisprudence is reasoning. Reasoning must be backed by certainty and clarity in order for it to be authentic. If in a case, a law is not specified--and the matter is not justifiable according to reason nor does it contain clarity--it will not be justifiable to follow conjecture and surmise. Guessing on issues and using a bias opinion on such matters will lead to destruction--since we are not worthy of such an act.

 Once Imam Muhammad Baqir A.S. had dialogues with Abu Hanifa who Used to practice analogy, Imam asked Abu Hanifa who is week among a man and a woman? Abu Hanifa replied a woman; Imam said then why a man has two shares in the willpower however a woman has one. Imam further Asked Abu Hanifa what is more important prayers or fasting? Abu Hanifa replied prayers, Imam said then why prayers are forbidden for woman in menses where as fasting is not, Imam asked him another question that what is more nijas, urine or semen, Abu Hanifa replied urine, Imam said then why Ghusal is wajib for semen but not for urine. Imam said thus analogy is not the way to deduce Islam jurisprudence.

 There is famous tradition of Holy Prophet Muhammad SAWW that I am leaving two valuable things behind me to which you all should refer, the holy Quran and Ahlul- Bayt (A.S.),hold on them and you will not be abandon.

 "Thus, our aim is not that we should philosophize or speculate about the rationale of Islamic laws and precepts. We aim to point out that since the teachings of Islam cover all spheres of human life, and since, on the basis of our belief in the doctrine of Divine justice, we know that these teachings are not extravagant and baseless, but are based upon truth and natural realities and are constituted on the basis of those realities, so if we come to know closely those realities - which have been systematically studied in the course of several centuries and their study has taken the form of scientific disciplines - we shall be better able to comprehend the meanings and purposes of the language of revelation (wahy), as we have seen in the study of ethics and theology."