OK Christians. your chance. Convince me of God.

[The Grand Nudger]

Sorry, was falling asleep at the keyboard, had to get some shuteye. I love the whole sufficiency and necessity bit. I understand that the example I offered is invalid, and I understand the concept of transposition, you're explaining either to me does nothing to answer the questions I've asked you. After pouring over the last few pages I finally think I've figured out my disconnect. When you begin with the "not a implies b, not b therefore Implies not A" I mistakenly assumed you were arguing a sufficient condition with the rule of inference for necessary conditions (I'm used to seeing "if and only if" in conditionals of necessary condition, which was not present in the initial premise, and in a subsequent post you mentioned that A is sufficient for B- which further confused me as I thought you were discussing the premise and not transposition itself) In essence, I thought you were asking me to assume that the premise satisfied sufficient condition and then argued from necessary condition. I wasn't dissatisfied with the relative truth value of the premise, but the way that I thought the premise had been followed by the rule of inference for a different sort of premise - mea culpa.

Am I mistaken in this, does a premise which contains a necessary condition not have to be expressed as "if and only if", as opposed to sufficient conditions "if"?

To elaborate upon where I may be confusing myself.

If you get an A, you will pass the class - sufficient
If and only if you get an A, you will pass the class - necessary

If the narrative is from other than god, you will find contradictions - sufficient
If and only if the narrative is from other than god, you will find contradictions - necessary

(why do you keep explaining shit which my posts would demonstrate that I understand perfectly well, btw, rather than answering any of my questions about the way the premise is worded? It took me forever to realize where ourt disconnect was and it just so happens that it looks like this is precisely how we ended up with a disconnect in the first place. It would be difficult for me to have been blathering on about transposition, modus ponens, and modus tollens these past few posts..and identifying your arguments as some variant of them if I was not aware of this...so why explain that to me, rather than correct me on how if and iff are somehow equivalent - which is actually something I don't understand? When you translate the A->B as a necessary condition colloquially are you not required to translate it as if and only if? IOW, I'm not unclear on the subject of modus tollens, but leary that your argument -specifically as you worded it- is not modus tollens)

This conversation has been great btw, led me to a webcrawl that yielded an awesome article on conditionals and language and the issues the two create when combined.