Logic has the problem that although two premises lead to one unambiguous conclusion, every conclusion can derive from many different premises. That is, although the route forwards is unambiguous, the route backwards isn’t.
This fact shows that logic isn’t a consistent system, which Bertrand Russell demonstrated in 1901 with “Russell’s paradox”. It means that logic can’t reach a single “truth”, but can only formulate countably infinite different possible “truths”. Logic itself is impotent in choosing between the countably infinite “truths”.
Fundamentally, logic is nothing but a system to avoid contradiction in each successive step of reasoning. It contains no obstacle for contradiction in several successive steps. One may well arrive to contradictions in a line of logical reasoning. This fact means that logic alone is impotent. It can actually reach any opinion, depending on what one assumes.
Logic itself can thus not act as a guiding star.