Thomas Aquinas

On Alchemy

Excerpted from Summa theologica 3.66.4.

I respond that it must be said that water is able to lose its purity and simplicity in two ways, in one way through mixing with another body, in another way through alteration.  And, moreover, either of these happens in two ways, namely through artifice and through nature.  Artifice, however, falls short of the operation of nature, because nature gives a substantial form, that which artifice is not able to do since all artificial forms are accidental unless, by chance, artifice applies the proper agent to the proper material, such as fire to something combustible, in which manner certain animals are produced from certain things by means of putrefaction.  Whatever transformation of water, then, is made through artifice, whether by mixing it or by altering it, the species of the water is not changed.  Thus baptism is able to take place in such water unless, by chance, the water is mixed artificially in so small an amount with another body that the mixture is rather something other than water; for example, mud is earth rather than water and diluted wine is wine rather than water.

original latin

Respondeo dicendum quod aqua suam puritatem et simplicitatem potest amittere dupliciter, uno modo, per mixtionem alterius corporis; alio modo, per alterationem. Utrumque autem horum contingit fieri dupliciter, scilicet per artem, et per naturam. Ars autem deficit ab operatione naturae, quia natura dat formam substantialem, quod ars facere non potest, sed omnes formae artificiales sunt accidentales; nisi forte apponendo proprium agens ad propriam materiam, sicut ignem combustibili, per quem modum a quibusdam quaedam animalia per putrefactionem generantur. Quaecumque igitur transmutatio circa aquam facta est per artem, sive commiscendo sive alterando, non transmutatur species aquae. Unde in tali aqua potest fieri Baptismus, nisi forte aqua admisceatur per artem in tam parva quantitate alicui corpori quod compositum magis sit aliud quam aqua; sicut lutum magis est terra quam aqua, et vinum lymphatum magis est vinum quam aqua.

Aliquando autem fit per naturam transmutatio aquae sine solutione speciei, et hoc tam per alterationem, sicut patet de aqua calefacta a sole; quam etiam per mixtionem, sicut patet de aqua fluminis turbida ex permixtione terrestrium partium.

Ad tertium dicendum quod aqua fluens de latere Christi pendentis in cruce non fuit humor phlegmaticus, ut quidam dixerunt. In tali enim humore non posset fieri Baptismus, sicut nec in sanguine animalis, aut in vino, aut in quocumque liquore alicuius plantae.

Ad quartum dicendum quod in lixivio, et in aquis sulphureorum balneorum, potest fieri Baptismus, quia tales aquae non incorporantur per artem vel naturam aliquibus corporibus mixtis, sed solum alterationem quandam recipiunt ex hoc quod transeunt per aliqua corpora.

Ad quintum dicendum quod aqua rosacea est liquor rosae resolutus. Unde in ea non potest fieri Baptismus. Et, eadem ratione, nec in aquis alchimicis, sicut in vino. Nec est eadem ratio de aquis pluvialibus, quae generantur ex maiori parte ex subtiliatione vaporum resolutorum ex aquis, minimum autem ibi est de liquoribus corporum mixtorum, qui tamen per huiusmodi sublimationem, virtute naturae, quae est fortior arte, resolvuntur in veram aquam, quod ars facere non potest.