No. Properly speaking, conscience is not a power, but an act because the application of knowledge to something is done by some act.
Conscientia, proprie loquendo, non est potentia, sed actus quia applicatio scientiae ad aliquid fit per aliquem actum.
For conscience, according to the very nature of the word, implies the relation of knowledge to something: for conscience may be resolved into "cum alio scientia," i.e. knowledge applied to an individual case.
Conscientia enim, secundum proprietatem vocabuli, importat ordinem scientiae ad aliquid: nam conscientia dicitur "cum alio scientia".
For conscience is said to witness, to bind, or incite, and also to accuse, torment, or rebuke. And all these follow the application of knowledge or science to what we do.
Dicitur enim conscientia testificari, ligare vel instigare, et etiam accusare vel remordere sive reprehendere. Et haec omnia consequuntur applicationem alicuius nostrae cognitionis vel scientiae ad ea quae agimus.
Conscience can be laid aside. But a power cannot be laid aside. Therefore conscience is not a power.
Conscientia deponi potest, non autem potentia. Ergo conscientia non est potentia.
Wherefore, properly speaking, conscience denominates an act. But since habit is a principle of act, sometimes the name conscience is given to the first natural habit: namely, "synderesis"; thus Jerome calls "synderesis" conscience (Gloss. Ezekiel 1:6); Basil [Hom. in princ. Proverb.], the "natural power of judgment," and Damascene [De Fide Orth. iv. 22] says that it is the "law of our intellect." For it is customary for causes and effects to be called after one another.
Unde proprie loquendo, conscientia nominat actum. Quia tamen habitus est principium actus, quandoque nomen conscientiae attribuitur primo habitui naturali: scilicet "synderesi", sicut Hieronymus, in Glossa Ezech. I, "synderesim" conscientiam nominat; et Basilius "naturale iudicatorium"; et Damascenus dicit quod est " intellectus nostri". Consuetum enim est quod causae et effectus per invicem nominentur.
Although an act does not always remain in itself, yet it always remains in its cause, which is power and habit. Now all the habits by which conscience is formed, although many, nevertheless have their efficacy from one first habit, the habit of first principles, which is called "synderesis". And for this special reason, this habit is sometimes called "conscience".
Actus, etsi non semper maneat in se, semper tamen manet in sua causa, quae est potentia et habitus. Habitus autem ex quibus conscientia informatur, etsi multi sint, omnes tamen efficaciam habent ab uno primo, scilicet ab habitu primorum principiorum, qui dicitur "synderesis". Unde specialiter hic habitus interdum "conscientia" nominatur.