Alphonsus

Caeremoniae ecclesiasticae, quae vulgo dicuntur sacramentalia, sunt actus externi religionis ad colendum Deum accommodati.

Ceremonies of the Church, which are commonly are called sacramentals, are external rites, which cultivate properly disposed worship of God.

- Alfonso Maria Ligouri, Theologia Moralis Vol.2. (Cincinnati:Benziger, 1888), 409.

paragraph #90

This is a definition of sacramentals which is significant because of the significance of the work itself, but also because it uses disposition in the definition. The work will go on to try to explain what power the sacramentals have in terms of their power to "excite pious devotion". While this may seem like a weak link, because the sacraments, the ordinary means of salvation, do not themselves provide the proper dispositions which are necessary for their fruitful reception, exciting pious devotion, that is, being properly disposed is incredibly important.

Furthermore, if we have a scientific understanding of what it means to be properly disposed, and we can say that the sacramentals help us to do that, we are coming closer to and understanding of the "spiritual effects" that the doctrinal definitions of sacramentals refer without explanation.