Two Latin Sentences-correct?

[JRoberts]

I wanted to translate the English, "It is a sin to write this. It is a sin to think thoughts that no one else has thought before."

I wrote:

Scelus scribere hoc est. Scelus cogitare cogitationes est quam nemo prius cogiterat.

Is this correct? I don't think I should have gone into an indirect statement, nor do I think the subjunctive was necessary (for the second sentence). However, I could easily be wrong .

Thanks .

[Beatus Pistor]

Scelus scribere hoc est. Scelus cogitare cogitationes est *quas*nemo prius *cogitavit*.
quas - relative which goes back to a plural noun(cogitationes).
Perfect Ind., your main verb is in the present.

[Amadeus]

Scelus scribere hoc est. Scelus cogitare cogitationes est *quas*nemo prius *cogitavit*.

And then, of course, we can do without the second "est."

«Scelus scribere hoc est. Scelus (ex?)cogitare cogitationes quas nemo antea cogitavit».