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Logic for Beginners

Khaos_Mage
Posts: 23,214
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2/20/2015 12:51:09 PM
Posted: 1 year ago
Take the following: (assume I believe this to be true)
P1 The purpose of civil marriage is to promote procreation from within the union
P2 Gays cannot procreate from within the union
C1 There is no purpose of civil marriage to be extended to gays

Now, ignoring the fact that P1 is blatantly false in today's day and age, is this an illogical thought process?
I say no, as what I believe is that P1 is the purpose, so it is irrelevant that the current state of affairs do not reflect my belief. That would be an is/ought fallacy for you to tell me this is an illogical statement.
An invalid one, because the government view marriage this way, yes, but not inherently illogical.

Am I correct?
My work here is, finally, done.
Envisage
Posts: 3,646
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2/20/2015 1:56:58 PM
Posted: 1 year ago
At 2/20/2015 12:51:09 PM, Khaos_Mage wrote:
Take the following: (assume I believe this to be true)
P1 The purpose of civil marriage is to promote procreation from within the union
P2 Gays cannot procreate from within the union
C1 There is no purpose of civil marriage to be extended to gays

C1 doesn't follow from the premises. If you are going to ci structure a formal syllogism then you need to use the same logicsl operators in the major premise and the conclusion.

You need to do something like a categorical for it to be valid e.g.

P1) All possible marriages promote procreation
P2) Same sex unions do not promote procreation
C) No same sex union is a possible marriage

Thus, you can see the operator "promote procreation" becomes a categorical proposition. And thus, this syllogism is a valid CAMESTRES (AEO-2) one of the form:

1.All P are Q
2. No R are Q
C. No R are P

http://en.m.wikipedia.org...

A colloquial example is:

1. All humans are moral
2. Zeus is not moral
C. Zeus is not a human

Now, ignoring the fact that P1 is blatantly false in today's day and age, is this an illogical thought process?
I say no, as what I believe is that P1 is the purpose, so it is irrelevant that the current state of affairs do not reflect my belief. That would be an is/ought fallacy for you to tell me this is an illogical statement.
An invalid one, because the government view marriage this way, yes, but not inherently illogical.

Am I correct?
Ajabi
Posts: 1,504
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2/20/2015 7:35:09 PM
Posted: 1 year ago
At 2/20/2015 1:56:58 PM, Envisage wrote:
At 2/20/2015 12:51:09 PM, Khaos_Mage wrote:
Take the following: (assume I believe this to be true)
P1 The purpose of civil marriage is to promote procreation from within the union
P2 Gays cannot procreate from within the union
C1 There is no purpose of civil marriage to be extended to gays


I think Propositional Logic would be easier to use here. You'd have to re-write the argument though, right now its invalid.

P1. If there is a civil marriage there must be the promotion of procreation from the Union
P2. Gay marriage does [is] not lead to the promotion of procreation
C1. Gay marriage is [cannot] be civil marriage.

P1. (C \/ P)
P2. ~P
C1. ~C

C1 doesn't follow from the premises. If you are going to ci structure a formal syllogism then you need to use the same logicsl operators in the major premise and the conclusion.

You need to do something like a categorical for it to be valid e.g.

P1) All possible marriages promote procreation
P2) Same sex unions do not promote procreation
C) No same sex union is a possible marriage

Thus, you can see the operator "promote procreation" becomes a categorical proposition. And thus, this syllogism is a valid CAMESTRES (AEO-2) one of the form:

1.All P are Q
2. No R are Q
C. No R are P

http://en.m.wikipedia.org...

A colloquial example is:

1. All humans are moral
2. Zeus is not moral
C. Zeus is not a human

Now, ignoring the fact that P1 is blatantly false in today's day and age, is this an illogical thought process?
I say no, as what I believe is that P1 is the purpose, so it is irrelevant that the current state of affairs do not reflect my belief. That would be an is/ought fallacy for you to tell me this is an illogical statement.
An invalid one, because the government view marriage this way, yes, but not inherently illogical.

Am I correct?