Are the objectives of Sharia a proof? And are they considered a source among the principles of Islamic jurisprudence?

The objectives of Sharia (definition) are not a stand-alone legal proof in themselves, but rather they enter into the proofs through two channels:

First: Justification by wisdom or benefit, where the objectives are integrated within the proof of analogy (Qiyas (definition)). Scholars of Usul (fundamentals of Islamic jurisprudence) have differed on the permissibility of justifying by wisdom; some have rejected it absolutely, while others have permitted it on condition that the wisdom is apparent and well-defined. The objectives are used in prioritizing between conflicting rulings, realizing specific conditions (tahqiq al-manat al-khass), and considering the consequences of actions.

Second: Undocumented public interest (Maslaha Mursala), which is an interest for which there is no specific textual evidence for its consideration or rejection, but rather it relies on the objectives and general principles of Sharia. Adopting it requires great caution and circumspection, and it is stipulated that it must not contradict a text (nass) or a consensus (ijma'), that it must contribute to the preservation of the objectives of Sharia, that it must not be in fixed rulings, and that it must not be opposed by a more preferable or equally preferable interest.