There are two broad principles in Usul al-Fiqh. One of these two is Al- Jam'u wat tawfeeq (reconciling two seemingly contradicting evidences). Scholars have chosen to use the phrase seemingly contradicting evidence because of the fact that the verses of the Quran and the sunnah of the Prophet (salallahu alayhi wa sallam) do not contradict one another. Allaah says "Do they not then consider the Quran carefully? Had it been from other than Allaah then you would surely have found there in many a contradictions," (Q4[Nisaa]:82).
Sometimes however, some verses or ahadeeth may appear to us as contradicting. For instance, Allaah says: "And divorced women shall wait (as regard their marriage for three menstrual periods," (Q2[Baqarah]:228). He also says in a different place in the Quran: "And for those who are pregnant, their 'Iddah (prescribed period is until they lay down their burden" (Q65[Talaq]:4). If we critically look at the first verse we see that Allaah gives a general ruling on divorced women whether she is pregnant or not. They must wait for three menstrual cycle before they can be able to remarry. Meanwhile the second verse states a totally different ruling from the first verse. The pregnant woman would not wait for three menstrual periods as required from all divorced women (as stated in the first verse). She would have to wait until she gives birth. Isn't this a contradiction? No! Certainly not! It is only our own weak understanding. To deal with this seeming contradiction which human mind may suggest with regards to the words of Allaah and the sunnah of Prophet Muhammad (salallahu alayhi wa sallam), scholars have established the principle of reconciliation.
The second broad principle is At tarjeeh. This means that if we are unable to reconcile these seemingly contradicting evidences through any of the principles under Al Jamu wa tawfeeq we resort to giving one evidence preference over the other. Hence, At-tarjeeh means giving preference to an evidence over and above another through any of the principles under at-tarjeeh. From next edition (insha Allaah) we shall start the study of the various principles upon which AI Jamu wat-tawfeeq (reconciliation) is done.
Subsequently, we study various principles that are employed before At tarjeeh (i.e. the preference of one evidence over and above a seemingly contradicting one) can be done.