From the Supplement, compiled after Aquinas’s death from his Commentary on the Sentences and transcribed here from the 1917 to 1922 printings. About the Supplement.
Text: Summa Theologiae, Supplement to the Third Part (Supplementum Tertiae Partis), transcribed from Internet Archive scans, translated by the Fathers of the English Dominican Province. The Supplement, compiled after Aquinas’s death from his earlier Commentary on the Sentences, in the same English Dominican translation as the Gutenberg Parts. Transcribed by Bibliotheca Catholica from the OCR of four Internet Archive scans of the pre-1931 printings (Questions 1 to 33 from the 1917 Washbourne and Benziger volume, 34 to 68 from the 1922 volume, 69 to 86 from the 1921 volume, and 87 to 99 from the 1922 Benziger volume), with OCR errors corrected and doubtful passages marked, not rewritten. 99 questions and 446 articles. The two appendices printed after Question 99 are not included. Sources, SHA-256 of each OCR file, and the method are in the source record. Rights: Public domain (US)
The Supplement is not a Project Gutenberg text. It is Bibliotheca Catholica’s transcription of public-domain scans at the Internet Archive; obvious OCR errors were corrected, and passages marked “OCR uncertain” could not be confidently corrected, so check them against the linked scan page.
Objection 1: It seems that an indulgence ought not to be granted for temporal help. Because the remission of sins is something spiritual. Now to exchange a spiritual for a temporal thing is simony. Therefore this ought not to be done.
Obj. 2: Further, Spiritual assistance is more necessary than temporal. But indulgences do not appear to be granted for spiritual assistance. Much less therefore ought they to be granted for temporal help.
On the contrary, stands the common custom of the Church in granting indulgences for pilgrimages and almsgiving.
I answer that, Temporal things are subordinate to spiritual matters, since we must make use of temporal things on account of spiritual things. Consequently an indulgence must not be granted for the sake of temporal matters as such, but in so far as they are subordinate to spiritual things: such as the quelling of the Church's enemies, who disturb her peace; or such as the building of a church, of a bridge, and other forms of almsgiving. It is therefore evident that there is no simony in these transactions, since a spiritual thing is exchanged, not for a temporal but for a spiritual commodity.
Hence the Reply to the First Objection is clear.
Reply Obj. 2: Indulgences can be, and sometimes are, granted even for purely spiritual matters. Thus Pope Innocent IV. granted an indulgence of ten days to all who prayed for the king of France; and in like manner sometimes the same indulgence is granted to those who preach a crusade as to those who take part in it.
Also online, linked only: the same translation at New Advent and the Latin text at Corpus Thomisticum. Neither is copied here.