The phrase "be demonstrable" means to be able to be shown or proven. There are several synonyms for this phrase, including "be provable," "be verifiable," "be evident," "be testable," "be confirmable," and "be ascertainable." These terms all convey the idea of something that can be supported or validated through evidence or observation. In scientific research, for example, it is crucial that any findings be demonstrable through rigorous testing and analysis. In other contexts, such as legal or academic writing, it is important to use precise language that accurately conveys the level of certainty or proof associated with a particular claim or assertion.