Nearly everything written about Philippine indigenous religion before the nineteenth century was written by men whose purpose was to end it. Fray Juan de Plasencia's Relacion de las Costumbres de los Tagalos, compiled in 1589, is the earliest systematic account of Tagalog belief and practice, and it was produced as a working document for missionaries: a catalogue of what to recognise and what to root out. Its detail is genuine and often the only detail there is. Its shape is not neutral. Practices are sorted into categories drawn from European demonology, the specialists are described as agents of the devil, and the whole is organised around the question of what must be forbidden. Reading such a source well means using it for what it observed while discounting what it assumed.
Later scholarship has done exactly that. Carolyn Brewer's work on shamanism, Catholicism and gender in the colonial Philippines reads the missionary record against itself to recover the standing of the babaylan and to show how deliberately that standing was dismantled, a female ritual specialist being both a rival authority and an offence to the order the friars brought with them. Damiana Eugenio's collections of Philippine myth gather narrative material from later oral sources and supply what the friars did not think worth recording. The atlas treats the tradition as living rather than extinct.