In the context of the declaration of independence, what does the author mean by “candid world”?

When the author utilizes the phrase "candid world" his intention is to establish a few specific attributes to the targeted audience, which is the rest of the world. Given the context in which the phrase is used, it's clear that he chooses the word "candid" to infer sincerity and honesty to this intended audience. By characterizing the receptors of the message in this way, the author is appealing to the audience's sense of morality. In the end, this rhetorical device persuades the audience into regarding the contents of the message as honest and sincere facts.

In summary, the author appeals to a "candid world" to make the audience also expect a sincere and honest message by persuading them into perceiving it in such a way.

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"the sandy walls seemed to collapse in on themselves"

and

"the bloodshot waters seemed to have no bottom"