I have question on a sentence from Newton's book: Opticks.

Page from "Opticks"

Specifically, I'm asking about the sentence Newton puts in italics:

By the Rays of Light I understand its least Parts, and those as well Successive in the same Lines as Contemporary in several Lines.

I have some queries about this:

  • I understand its least parts.

    Does it mean that Newton fully understand some part of light? or does it mean that Newton partly understand light?

  • those

    Does those match with least parts? or the Rays of Light? (those comes after and. That's why I wonder.)

  • Successive

    Is it correct to capitalize first letter in the words Rays, Light, Successive, Lines, Contemporary?

Here are my guesses:

  1. Newton understands the smallest parts of the Rays of Light.
  2. Successive, Lines, and Contemporary are all used as nouns.
  3. Newton understands that the Rays of Light are Successive and Contemporary (There is no and after same Lines, so this guess probably wrong)
  4. The structure of sentence is "By [noun] [sentence] and those as [noun], [noun]"

Am I right?

  • Taeyun, I've made some revisions because it's very important when quoting something not to alter what you are quoting by inserting brackets, punctuation, or anything else which might alter its meaning. I've also added the original because it could help. I suspect that all your questions are answered in the rest of Definition 1 (of which the image shows the first half-dozen lines).
    – Andrew Leach
    Commented Oct 18, 2017 at 10:26
  • @AndrewLeach Thank you very much. Reading rest of Definition 1 may answer my question. But I wonder if it's possible to tell the meaning of first sentence from just first sentence.
    – Taeyun
    Commented Oct 18, 2017 at 10:31
  • Hello, Taeyun. There are several reasons why this isn't a good fit for the ELU question model, prime among which are the fact that it consists of multiple questions, is essentially asking for a 'comprehension'-style analysis, and is dealing with a peripheral (at the same time old, cutting-edge, and scientific) register. It's a great (multiple-) question, but I feel there are more suitable places to ask (or investigate) it. A history-of-science site? // As a start, I'd suggest 'mean' for 'understand', the latter used because the theory as well as the terminology is being introduced. Commented Oct 18, 2017 at 10:32
  • So: that said, it will possible to deal with, say, "I understand its least parts". The capitalisation of nouns has already been dealt with on ELU; as it was simply used to denote a word as important, that can be easily applied to adjectives too. I suggest only asking about the part you most need to know about. Just edit the question to remove the other parts.
    – Andrew Leach
    Commented Oct 18, 2017 at 10:37
  • 1
    This hardly opens up the site to claims of mediocrity or triviality as some questions do. And its not likely to invite a flood of other questions asking for interpretations of early scientific texts (where, as @Max says in his answer, there are problems with scientific understanding of at least equal magnitude to those involved with choice of language to express the analyses). But it remains peripheral and, as Sällström (Max's link) concedes, POB ('What he had in mind was probably some kind of '). / ... / On balance, I'd not worry about it. Commented Oct 18, 2017 at 11:09

1 Answer 1


According to this analysis by Pehr Sällström, when Newton wrote "I understand its least parts", he meant "I understand its smallest constituents".

From that page:

What he had in mind was probably some kind of atomic constituents of the hypothetical enigmatic entity “light”. Accordingly, we nowadays speak of photons, a photon having its characteristic frequency (or corresponding wavelength, if you prefer). Any light beam is a flux of a great many independent photons...

The analysis doesn't state what those, successive, contemporary etc are referring to, but my take on it is that those means "the others", so that the whole sentence "By the Rays of Light I understand its least Parts, and those as well Successive in the same Lines, as Contemporary in several Lines." could be rewritten as

Regarding the rays of light, I understand the smallest constituents of them, and the ones that come before or after them within the same rays. Further, these are contemporary to, ie of the same basic type but with some small difference, as the constituents in the other rays of light."

This is just my analysis and may be incorrect.

He didn't, as it happens, understand them - I don't think anyone does, fully, even today - but he thought that he did.

I think that linked analysis will help with your other questions about this text.

As far as capitalisation goes, it's not correct by modern standards. As for the standards of the day, they weren't as well established as they are today: there weren't a great number of books written, and certainly not books like Newtons great works of "natural philosophy", as science was called at that time. It looks like capitalisation is used as a way of emphasising words, like we would use italics or boldface today. This is covered in more detail in this other question.

  • Thank you very much. I modified the question to ask only one question, but after the modification, I read your answer, so I reverted the question again to match your answer. Thanks again!
    – Taeyun
    Commented Oct 18, 2017 at 10:55
  • Newtons 'successive' means sequential: in the same space but at different times, while 'contemporary' means parallel: in a different place but at the same time.
    – AmI
    Commented Oct 18, 2017 at 16:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.