Source: p 114, A Little History of Philosophy (2011 ed; but 2012 Reprint ed extant) by Nigel Warburton PhD in Philosophy (Cambridge)
If Kant is right, this is a breakthrough. Before him philosophers investigating the nature of reality treated it simply as something beyond us that causes our experience. Then the difficulty was how we could ever get access to that reality to say anything meaningful about it that was more than just guesswork. His great insight was that we could, by the power of reason, discover features of our own minds that tint all our experience. Sitting in an armchair thinking hard, we could make discoveries about reality that had to be true, yet weren’t just true by definition: they could be informative. He believed that by logical argument he had done the equivalent of proving that the world must necessarily appear pink to us. He’d not only proved that we are wearing rose-tinted spectacles, [1.] but had also made new discoveries about the various shades of pink that [2.] these glasses contribute to all experience.
I do not feel prepared yet to tackle Kant; so I do not know if this allegory in 1 originates from Kant or the author Dr Warburton.
What does the allegory of various shades of pink mean?
I also do not understand why in 2, these glasses is expressed as a Plural (in Number) Noun Phrase. According to Kant, (each person's) experience necessitates, and so is tinted by, the mind that metaphorised as the rose-tinted spectacles. So should not each person should be tinted by only ONE pair of rose-tinted sunglasses, and not the Plural Number as 2 implies?