This determined at once the strength and the weakness, the achievement and the limitation, of the materialist theory. What pushed that theory forward was, so Engels writes in Ludwig Feuerbach, "the powerful and ever more rapidly onrushing progress of science and industry".

From Materialism and the Dialectical Method (Maurice Cornforth)

I don't know the use of the word "so" in the text. Is it the same as the word "as"? Or does it mean "thus"?

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    It means the author is about to quote something that Engels wrote. Here, it could be replaced by as. Commented Oct 26, 2022 at 15:36
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    It's relatively "erudite" and "dated" phrasing, within which context I have no doubt that at once in the preceding sentence doesn't have its normal current sense of immediately. It just means both, at the same time, with no implication as to how swiftly the "scientific investigation of nature" (from earlier sentence not cited here) identified said strengths and the weaknesses, etc. Commented Oct 27, 2022 at 13:03

2 Answers 2


"So" is a somewhat magical word. It has subtle connotations that other words do not.

It is true that in your example, "so" and "as" are lexically synonymous. But replacing "so" with "as" slightly changes the connotation.

At the time the book was written, Friedrich Engels was one of the rising stars of philosophy. The use of the word "so" suggests that the quotation is unarguable because Engels said it. It subtly suggests that the quote from Engels is an established fact and not just a belief.

A similar connotation can be found in at least one idiom:

So it is said...

As stated, "so" can be lexically replaced by "as."

As it is said...

But I believe those two phrases have slightly different meanings to native English speakers. Used as a response in a conversation ("I've heard that red skies at night means it won't rain!" ... "So it is said."), the first can carry a subtle disbelief about what is being said or even be used as a dismissal of the conversation (such as a parent who is only half-listening to an excited child).

Whereas the second is simply an acknowledgement of the statement citation ("I've heard that red skies at night means it won't rain!" ... "As it is said." No native English speaker would use the phrase this way, it's unnatural. But the response could naturally be, "As it is said in the old sea chant.").

That the subtle connotation of "so" in this idiom is different than what I believe exists in the quote from Cornforth simply underscores the somewhat magical nature of "so." It is often used artistically where "as" is more technical in nature (fewer connotations). The connotations of "so" are dependent on the context of the word. Indeed, the word "so" may only have the connotation I'm recommending because I know who Engels was and of his importance to the development of socialist philosophy. But, so would Cornsforth and, likely, his expected audience. Therein lies the artistry — and magic — of the word.

Maybe I'm wrong (and it's OK to down vote me if I am), but I do not believe the word "as" carries that authoritative connotation as found with the word "so" in Cornforth's quote. And while replacing "so" with "as" would not change the inherent meaning of the sentence, I believe it would remove some of the artistry of the text and some of the certainty Cornforth was trying to convey.

In short: I believe Cornforth used the word "so" intentionally and for a reason that is not wholly duplicated by the word "as."

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    I think you raise interesting points which were well worth posting, so I'm voting up. I frequently leave out things I feel would make an answer more complete because I'm uncertain where the line between fact and opinion lies in the given case.
    – PRL75
    Commented Oct 26, 2022 at 18:08
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    +1 I love this kind of analysis, and IMO you're right. It's really important for learners to know that two things which are grammatically interchangeable aren't necessarily semantically identical.
    – gotube
    Commented Oct 26, 2022 at 19:03
  • Who is Engles?? Commented Oct 26, 2022 at 22:12
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    @RonaldSole Yeah... that happens to me sometimes. Imperfection is rather inconvenient. Yours was an obtuse reference to my misspelling, but thanks anyway for pointing it out.
    – JBH
    Commented Oct 27, 2022 at 0:54
  • "So" also gives to me more of a suggestion of paraphrase, rather than direct quote. Commented Oct 27, 2022 at 3:23

In this context, yes, the word 'so' is exactly synonymous with 'as'.

In other, similar cases it can mean the same as 'thus' or 'therefore'.

e.g. Engels believes [x] so he writes [statement of belief in x].

  • "Exactly synonymous" or grammatically equivalent? See JBH's answer for what I'm talking about
    – gotube
    Commented Oct 26, 2022 at 19:04

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