It's why it is so important to substantiate both the plot, and its connection to Iran.
Thus, catharsis, in a physiological sense, has been difficult to substantiate, but the results are by no means conclusive.
So, President Obama does right by making every effort to substantiate the charges against Assad.
1650s, "to make real, to give substance to," from Modern Latin substantiatus, past participle of substantiare, from Latin substantia (see substance). Meaning "to demonstrate or prove" is attested from 1803. Related: Substantiated; substantiating.