When it comes to justifying an argument or decision, it is important to have a clear and logical explanation. The phrase "more rationale" refers to the need for additional reasons or justifications in support of a particular viewpoint. Some synonyms for this phrase include "further justification," "additional reasoning," or "greater logic." These synonyms all emphasize the importance of thoroughly explaining and providing evidence for a particular claim or conclusion. By using these alternative phrases, writers and speakers can effectively convey the need for more evidence and support, and demonstrate their commitment to sound reasoning and logical thinking.