d thy God."

_I answer that,_ As stated above (A. 1), to tempt a person is to put
him to a test. Now one never tests that of which one is certain.
Wherefore all temptation proceeds from some ignorance or doubt,
either in the tempter (as when one tests a thing in order to know its
qualities), or in others (as when one tests a thing in order to prove
it to others), and in this latter way God is said to tempt us. Now it
is a sin to be ignorant of or to doubt that which pertains to God's
perfection. Wherefore it is evident that it is a sin to tempt God in
order that the tempter himself may know God's power.

On the other hand, if one were to test that which pertains to the
divine perfection, not in order to know it oneself, but to prove it
to others: this is not tempting God, provided there be just motive of
urgency, or a pious motive of usefulness, and other requisite
conditions. For thus did the apostles ask the Lord that signs might
be wrought in the name of Jesus Christ, as related in Acts 4:30, in
order, to wit, that Christ's power might be made manifest to
unbelievers.

Reply Obj. 1: The paying of tithes was prescribed in the Law, as
stated above (Q. 87, A. 1). Hence there was a motive of urgency to
pay it, through the obligation of the Law, and also a motive of
usefulness, as stated in the text quoted--"that there may be meat in
God's house": wherefore they did not tempt God by paying tithes. The
words that follow, "and try Me," are not to be understood causally,
as though they had to pay tithes in order to try if "God would open
the flood-gates of heaven," but consecutively, because, to wit, if
they paid tithes, they would prove by experience the favors which
God would shower upon them.

Reply Obj. 2: There is a twofold knowledge of God's goodness or will.
One is speculative and as to this it is not lawful to doubt or to
prove whether God's will be good, or whether God is sweet. The other
knowledge of God's will or goodness is effective or experimental and
thereby a man experiences in himself the taste of God's sweetness,
and complacency in God's will, as Dionysius says of Hierotheos (Div.
Nom. ii) that "he learnt divine things through experience of them."
It is in this way that we are told to prove God's will, and to taste
His sweetness.

Reply Obj. 3: God wished to give a sign to Achaz, not for him alone,
but for the instruction of the whole people. Hence he was reproved
because, by refusing to ask a sign,