2. The Subject Matter of ‘Ilm al-Usūl and Its Benefits
Traditionally for every science a subject matter is usually mentioned, and what is intended by the subject matter is a definition which encompasses all of the sciences particularities. In this light, the discussions of the particularities (within the said science) revolve and are based on the subject matter, just like words would be considered the subject matter of grammar.
On this basis the Usūlī scholars have endeavoured to clarify the subject matter of this science, with a number of earlier scholars (mutaqadimūn) positing the subject matter to be “the four proofs, The Qur’ān, the Sunna, the consensus and reason”. However this has been criticised as the subject matter of “the four sources” does not encompass all of the particularities discussed within ‘Ilm al-Usūl. For example, the matter of rational necessitation (istilzāmāt) whose subject matter is law, if it is said “does the obligation of a law necessitate the impermissibility of it’s opposite or not?” (would be excluded from this definition. Or the matter of speculative indicators (al-amārāt al-dhannī), whose subject matter is predominantly the probative force of a thing, would also be excluded from such a definition. Similarly prevalence (shuhra) and the solitary tradition would be excluded. And the matter of procedural principles (usūl al-‘amalīyyah) whose subject matter is doubt in the existence of an obligation in its various forms would also be considered outside of the definition (of “the four sources”).
It is for this reason that a group of Usῡli scholars have mentioned that ‘Ilm al-Usūl does not have only one subject matter, neither is it necessary for it to only have one subject matter which encompasses all of its particularities. It is possible to justify the first definition that “proof” can be the potential subject matter, however only by not limiting the jurisdiction of “source” to four. Thus we may say “the subject matter of ‘Ilm al-Usūl is whatever is anticipated to be a proof or a shared element in the process of the derivation of the divine law and its argumentation”. The discussion in every Usūli particular would revolve around the anticipation of that thing being a proof for the divine law; it shall concentrate on the (validity of the) proofness of that proof and it’s employment in arguing for the affirmation of (the divine law) or it’s negation. So the discussions (within ‘Ilm al-Usūl) on the probative force of the prima facie, or solitary tradition, or prevalence, are discussions (strictly) to do with its proofness [i.e. the validity of it being used as a proof in the derivation of the divine law]. Similarly, the discussion on whether the obligation of an action rationally necessitates the impermissibility of its opposite looks at the proofness (of the connection) between the obligation of an action and the impermissibility of it’s opposite. Also, the matter of the procedural principles through which doubt in an obligation, or the exoneration in the absence of a clear command (bayān), is discussed [similarly in regards to its proofness]. On this basis it is correct to assert that the subject matter of ‘Ilm al-Usūl is “the shared proofs employed in the derivation of divine law”, and all discussions within this science continuously revolve around the proofness (of these “shared proofs”).
It has been made clear from what has passed that ‘Ilm al-Usūl has a significant benefit in the process of demonstrative jurisprudence. This is due to the fact that the jurist relies on two types of preliminaries in his (process of) demonstrative jurisprudence.
First Type: The specific elements limited to one particular matter, for example, a tradition that is relevant to one specific matter, or the prima facie of that tradition in affirming the desired divine law (in this one specific matter), or the absence of any contrary traditions (in this one specific matter).
Second Type: The shared elements which are employed in the demonstration of a number of different matters and are not limited to one specific subject of jurisprudence, like the probativity of a solitary tradition, or the probativity of the prima facie applied to verbal evidence.
The first type of preliminaries aids the jurist in dealing with that specific matter, as it is connected to that matter alone. However, the second type, in contrary to the first, are not limited to a specific jurisprudential issue and are considered to be outside the domain of jurisprudence. It is these independent discussions that are referred to as ‘Ilm al-Usūl. In the same proportion that jurisprudential discussions expanded due to increased gradual attention to it, ‘Ilm al-Usūl has similarly expanded and increased in its importance [over time]. Therefore this statement is correct that says the role of ‘Ilm al-Usūl in relation to demonstrative jurisprudence resembles, in a general sense, the role of Logic in relation to the process of reasoning. In this perspective, Logic doesn’t deal with specific chapters of reasoning but rather through it’s shared elements deals with it in its entirety, similarly ‘Ilm al-Usūl deals specifically with demonstrative jurisprudence through it’s shared elements which are applicable in every chapter of jurisprudence, not just a few.