The phrase "simple truth" can refer to a concept that is straightforward and easy to understand, without any complex details or nuances. Some synonyms for the phrase "simple truth" include plain fact, basic reality, fundamental veracity, and essential certainty. Other alternatives could be unambiguous certainty, straightforward verity, or plain honesty. These phrases suggest a directness and clarity that make it easy to comprehend a particular idea or situation. Using these synonyms can help to emphasize the simplicity of a concept, avoiding the need for convoluted explanations or complicated language. Ultimately, the use of such synonyms helps to convey a clear and direct message to the audience.