Are these sentences accepted in terms of grammar?

[roseriver1012]

[FONT=楷体_GB2312]The sentences are as follows:[/FONT]
[FONT=楷体_GB2312]I think， therefore I exist.[/FONT]
[FONT=楷体_GB2312][FONT=隶书]Charles Lindbergh, for his attempt at a solo transatlantic flight, was very reluctant to have any extra weight on his plane, he therefore refused to carry even a pound of mail, despite being offered $1,000 to do so.[/FONT]
[/FONT]
[FONT=楷体_GB2312]I always think that "therefore" is only an adverb. Can it be possible that it is also used as a conjunction? Thanks for your help![/FONT]

 

[TheParser]

[FONT=楷体_GB2312]The sentences are as follows:[/FONT]
[FONT=楷体_GB2312]I think， therefore I exist.[/FONT]
[FONT=楷体_GB2312][FONT=隶书]Charles Lindbergh, for his attempt at a solo transatlantic flight, was very reluctant to have any extra weight on his plane, he therefore refused to carry even a pound of mail, despite being offered $1,000 to do so.[/FONT]
[/FONT]
[FONT=楷体_GB2312]I always think that "therefore" is only an adverb. Can it be possible that it is also used as a conjunction? Thanks for your help![/FONT]

***** NOT A TEACHER *****

Good morning, Roseriver.

(1) I believe that most books call "therefore" either a "transitional adverb" or "conjunctive adverb."

(a) In other words, it does the job of a conjunction + an adverb.

(2) Mr. Lindbergh was very reluctant to have any extra weight on his plane; therefore he refused to carry even a pound of mail/ weight on his plane; he therefore refused to ....

(a) I think most teachers require a semicolon after "plane."

(b) "therefore" connects "he refused to carry even a pound of mail" with "Mr. Lindbergh was ... on his plane."

(c) And as an adverb it modifies "refused."

Thank you.

*****

P. S. Some people would use commas -- it's up to you. Your decision.

on his plane; therefore, he refused. ....

on his plane; he, therefore, refused. ....

I think (only think) that most writers nowadays would NOT use those commas.

 

[Raymott]

[FONT=楷体_GB2312]The sentences are as follows:[/FONT]
[FONT=楷体_GB2312]I think，therefore I exist.[/FONT]


[FONT=楷体_GB2312][FONT=隶书]Charles Lindbergh, for his attempt at a solo transatlantic flight, was very reluctant to have any extra weight on his plane. He therefore refused to carry even a pound of mail, despite being offered $1,000 to do so.[/FONT]
[/FONT]
[FONT=楷体_GB2312]I always think that "therefore" is only an adverb. Can it be possible that it is also used as a conjunction? Thanks for your help![/FONT]

The quote in Latin by Descartes "Cogito, ergo sum" is often translated in English as "I think, therefore I am". But "exist" also makes sense.