Scientist: Any theory that is to be taken seriously must affect our perception of the world.
Conclusion
Just because a theory affects our perception of the world does not show that we should take it seriously.
Evidence (to see this)
Look at astrology. (apparently, the author thinks that astrology affects our perception of the world but shouldn't be taken seriously)
Evaluate
The first sentence gives us a conditional rule, signified by the sufficient indicator any.
taken seriously → affects our perception
The author then pivots by saying, even though [affects perception] is necessary, it's not sufficient. The author's actual words are:
If we thought that A was, in itself, enough to establish B, we'd be saying that A is sufficient to prove B.
So our author is saying, this condition of [affects our perception] is not sufficient to establish that [theory taken seriously]. To demonstrate this, he then cites the example of astrology, using Support Language:
To see X, one need only consider Y.
Goal
The point of mentioning astrology was to provide evidence that [affects our perception] is not in itself enough for [theory to be taken seriously].
If we're trying to prove that X does not guarantee Y then we want an example where X is true but Y isn't.
So, astrology was an example of a theory that affects our perception but shouldn't be taken seriously.