Use the passage below to answer all parts of the question that follows. "Unluckily, the accounts of Spanish authors concerning Maya mythology do not agree with the representations of the gods delineated [described precisely] in the codices. That the three codices have a mythology in common is certain. Again, great difficulty is found in comparing the deities of the codices with those represented by the carved and stucco bas-reliefs of the Maya region. It will thus be seen that very considerable difficulties beset the student in this mythological sphere. So few data have yet been collected regarding the Maya mythology that to dogmatize [represent as absolute truth] upon any subject connected with it would indeed be rash [impulsive]. But much has been accomplished in the past few decades, and evidence is slowly but surely accumulating from which sound conclusions can be drawn."
Lewis Spence, The Myths of Mexico and Peru, 1913

QUESTION: Describe Spence's claim in the passage above.