Los historiadores alfonsíes se plantearon los mismos problemas que han interesado a historiadores de todos los tiempos. Buscaron documentación y determinaron cuál era la más fiable para su propósito. Sin embargo, la jerarquía otorgada a algunas fuentes no era un argumento suficiente para incorporar hechos en el relato de la historia, ni era prueba de que lo que se iba a narrar era verdadero. Una vez escogida, la autoridad se daba por buena, pero se explicaba y confrontaba con otras autoridades. Era imprescindible un ejercicio de raciocinio para comprobar la veracidad, la lógica de lo leído en las fuentes, así como la exposición razonada de los hechos, una narración adecuada a la trascendencia de lo que se narraba. La prueba se construía también con una redacción coherente.
The Alphonsine historians questioned the same problems that have interested historians througho0ut time. They searched for documentation and determined which was the most reliable for their purpose. However, the hierarchy granted to some sources was not enough argument for incorporating facts in the narrative of history, nor was it proof that what was going to be told was true. Once chosen, the authoritative source was positively assessed, but it was explained and confronted with other sources, whenever possible. A reasoning exercise was essential to check the veracity, the logic of what was read in the sources, and a reasoned exposition of the facts was crucial, a story adapted to the needs, to the transcendence of what was narrated. The truthfulness is constructed with coherent wording