The contrapositive


#1

The contrapositive is a logical truth. It means, in logic speak, that if A implies B, then NOT B implies NOT A.

(NOT A is true if A is false, and false if A is true. A implies B means that if A is true then B must be true, whereas if A is false, B could be true or false).

You can prove this with a truth table, but I won’t do it here. It is common sense, when you use an example.

Like if I say, “IF it is raining THEN I will use an umbrella.” You can write this in logic speak as “rain” implies “umbrella”. If you then see me without an umbrella, then you know that it must not have been raining. Otherwise my statement would have been false. So you can also conclude, from my original statement, that “IF I don’t use an umbrella THEN it is not raining.” That’s the contrapositive.

Why does this matter to Catholics? Well there are a lot of Protestants who say “You don’t need to do works to be saved.” So you say to them, so why do you bother doing good works? Why is Jesus telling us to do good works if He is gonna let us into heaven anyway, whether we do them or not? And the Protestant may reply, “People who are saved will do good works out of gratitude to God.” Or something like that.

So let’s convert their last statement into logic speak.

“Saved” implies “works”.

Therefore, by the contrapositive, “NOT works” implies “NOT saved”

In other words, if you don’t do good works then you’re not saved. They said it themselves.

Well lucky that’s true because that’s what Jesus was trying to say in Matt 25:31-46 ay? I guess Jesus knew logic.


#2

[quote=Flopfoot]The contrapositive is a logical truth. It means, in logic speak, that if A implies B, then NOT B implies NOT A.

(NOT A is true if A is false, and false if A is true. A implies B means that if A is true then B must be true, whereas if A is false, B could be true or false).

You can prove this with a truth table, but I won’t do it here. It is common sense, when you use an example.

Like if I say, “IF it is raining THEN I will use an umbrella.” You can write this in logic speak as “rain” implies “umbrella”. If you then see me without an umbrella, then you know that it must not have been raining. Otherwise my statement would have been false. So you can also conclude, from my original statement, that “IF I don’t use an umbrella THEN it is not raining.” That’s the contrapositive.

Why does this matter to Catholics? Well there are a lot of Protestants who say “You don’t need to do works to be saved.” So you say to them, so why do you bother doing good works? Why is Jesus telling us to do good works if He is gonna let us into heaven anyway, whether we do them or not? And the Protestant may reply, “People who are saved will do good works out of gratitude to God.” Or something like that.

So let’s convert their last statement into logic speak.

“Saved” implies “works”.

Therefore, by the contrapositive, “NOT works” implies “NOT saved”

In other words, if you don’t do good works then you’re not saved. They said it themselves.

Well lucky that’s true because that’s what Jesus was trying to say in Matt 25:31-46 ay? I guess Jesus knew logic.
[/quote]

Hi Flopfoot,
I love it.
You remind me of my “Drill Instructor” in Boot Camp…always launching us into some form of conditioning.
That is an excellent form of "Mind, Soul, and Spirit excercise which helps clean out the cob-webs in the dark corners of my brain.

:smiley:
God Bless you

gusano


#3

What you’ve said is highly logical, and most mainstream Protestants would agree. The only trouble is that their objection to Catholic doctrine (or what they think is Catholic doctrine) is much more subtle usually. They object to the idea that works play a part in us actually gaining salvation. They think they’re a necessary evidence of salvation and nothing more. They’re fine with the idea that faith plays a part in gaining salvation, though. I don’t really understand why faith has to be so separated from works here, but it’s the way my Protestant upbringing taught me to look at things. Apparently faith can “earn” heaven, but good works can’t. When you’ve held an idea for a very long time, it’s hard to objectively criticize it.

What the whole Protestant argument usually ignores, though, is grace. Ephesians 2 says we are saved by grace through faith, and that faith doesn’t come from us. Paul goes on to write that we were created for good works. I don’t think he means to separate faith and good works here, but rather imply that they’re almost one and the same. When arguing against the Catholic strawmen they set up, Protestants ignore the whole grace aspect of things, even when they don’t ignore grace in their own theology. It shouldn’t be hard to accept that grace causes faith and good works. Both faith and good works, therefore, are the means of salvation. The means do not negate the source of salvation, which is grace.


#4

Let’s try this logic on something else.

“Infallible statement” implies “accepted by the Church”

(From Lumen Gentium 25, “To these [infallible] definitions the assent of the Church can never be wanting, on account of the activity of that same Holy Spirit, by which the whole flock of Christ is preserved and progresses in unity of faith.”)

Therefore, “not accepted by the Church” implies “not infallible”.


#5

[quote=Kristina P.]What the whole Protestant argument usually ignores, though, is grace. Ephesians 2 says we are saved by grace through faith, and that faith doesn’t come from us.
[/quote]

Actually, if I may:

Ephesians 2:8-9

For by grace you have been saved through faith, and this is not from you; it is the gift of God;it is not from works, so no one may boast.

If you note, ‘though faith’ is parenthical to it. The sentence could function completely without ‘though faith,’ but though faith makes ‘grace,’ clearer. “And this is not from you.” Wouldn’t this refer back to grace? I mean, it may not, I don’t know how the CC interprets it, but that fits well with grace, because grace it not from us, it is from God. So perhaps it says and that grace doesn’t come from us. What do you think?

Therefore, “not accepted by the Church” implies “not infallible”.

Only if we agree that the only infallible body/person is the Church.


#6

[quote=RobNY]Actually, if I may:

Ephesians 2:8-9

If you note, ‘though faith’ is parenthical to it. The sentence could function completely without ‘though faith,’ but though faith makes ‘grace,’ clearer. “And this is not from you.” Wouldn’t this refer back to grace? I mean, it may not, I don’t know how the CC interprets it, but that fits well with grace, because grace it not from us, it is from God. So perhaps it says and that grace doesn’t come from us. What do you think?

Only if we agree that the only infallible body/person is the Church.
[/quote]

I believe it says; Neither Grace nor Faith comes from us.
It comes to us.

Jesus Christ came into this world to OFFER HIS LIFE as a ransom for many…
The problem is that since we are all sons of Adam we have a propensity for twisted logic, which means that we are
clever and full of human trickery.

People will take HIS OFFER and “fine tune it”, “improve it”, “alter it” remove parts, add parts…
and promote it as “christianity”

… I agree that the only infallible body/ person is The Church, (1 Tim. 3: 15)
Meaning, The Apostolic Teaching Authority of the Church consisting of The Magisterium and our Pope.

gusano


#7

[quote=RobNY]Only if we agree that the only infallible body/person is the Church.
[/quote]

My point is that contrapositive reasoning doesn’t always work so well on matters of religion, as opposed to matters of mathematics.


#8

[quote=RobNY]Actually, if I may:

Ephesians 2:8-9

If you note, ‘though faith’ is parenthical to it. The sentence could function completely without ‘though faith,’ but though faith makes ‘grace,’ clearer. “And this is not from you.” Wouldn’t this refer back to grace? I mean, it may not, I don’t know how the CC interprets it, but that fits well with grace, because grace it not from us, it is from God. So perhaps it says and that grace doesn’t come from us. What do you think?
[/quote]

That grace does not, can not, will not, must not come from us.

Grace of its very nature something on which no man ever at any time can have, has had, did have, could have, the ghost of a shadow of a claim. Anything less strikes me as paganism - it eats away at the sovereignty & freedom & holiness & Love of God, because it does not allow God to be uncontrained: instead, He becomes our debtor.

If God in His sovereignty and unlimited dominion wishes by His own good pleasure to upset the theologisings of those who want to leave no place for Him to be our debtor, ISTM that what He Wills, is what goes - that He must be sovereign enough to behave as though He were not sovereign: I think this is what happens in the Incarnation & later. But he can act “unsovereignly” only because He is sovereign in all His ways - His behaving as though He were not Who He is, is another way of showing that He is indeed Who He is.

And His grace is in all this; it is never other than wholly “of God”, whatever else it may be ##

Only if we agree that the only infallible body/person is the Church.


#9

[quote=Gottle of Geer]## That grace does not, can not, will not, must not come from us.

Grace of its very nature something on which
no man ever at any time can have
has had, did have, could have, the ghost of a shadow of a claim. Anything less strikes me as paganism -
[/quote]

I am beginning to wonder if you were absent from school on the day GOD, & GOD’S GRACE were introduced.
or maybe you went to a different school than some of us. :slight_smile:

it eats away at the sovereignty & freedom & holiness & Love of God,

How can anything created or man made “eat away” at the sovereignty, freedom, holiness, and Love of God ?
are you suggesting that God is vulnerable, and can be deminished by what He has made ?
Looks to me like someone has been tampering with your concept of “god.”

because it does not allow God to be uncontrained: instead, He becomes our debtor.

If God in His sovereignty and unlimited dominion wishes by His own good pleasure to upset the theologisings of those who want to leave no place for Him to be our debtor, ISTM that what He Wills, is what goes - that
He must be sovereign enough to behave as though He were not sovereign: I think this is what happens in the Incarnation & later.
But he can act “unsovereignly” only because He is sovereign in all His ways - His behaving as though He were not Who He is, is another way of showing that He is indeed Who He is.

And His grace is in all this; it is never other than wholly “of God”, whatever else it may be ##

Now there (in-bold) I agree with you…There is Hope !
Just as THE SOVEREIGN GOD chose to become a tiny baby in The Virgin’s Womb, …He further humbled himself
to be obedient and accept death on a cross (a curse)
and even after that, he humbled himself further to become a small piece of bread…
to be eaten and Adored by a People of his own,

and also receive the ridicule of a people
who call themselves by his name.

and he remains PATIENT at Hebrews 10: 13, …Why?
Because He is sovereign.
He has eternity in his palm.

May God give you
Grace to have forever,

gusano


#10

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