"warranted by the Constitution..."See in text(Text of Lincoln's Proclamation)
The participle “warranted” refers to an act that has been approved, justified, or sanctioned by a governing body or authority. Lincoln concludes his proclamation by again emphasizing that the Constitution allows him this power. This move not only achieves his aim to emancipate the slaves but also invokes the authority of the US Constitution.
"countervailing..."See in text(Text of Lincoln's Proclamation)
The adjective “countervailing” derives from the verb “to countervail,” which means that something is equivalent to another in value or that one force has been balanced against another. Since it modifies the noun “testimony,” Lincoln is stating that without strong evidence against their allegiance to the Union, such states are not considered in rebellion. The inclusion here of the parenthetical phrase “in the absence of strong countervailing testimony” possibly serves as an appeal to particular audience members who would have sought evidence of treason.
"to wit..."See in text(Text of Lincoln's Proclamation)
The noun “wit” refers to the faculty of the mind, or someone’s ability to think, reason, and understand. The verb form here introduces Lincoln’s previous proclamation in order to inform audiences that they ought to be aware of the context in which the final Emancipation Proclamation will be issued.
"a proclamation..."See in text(Text of Lincoln's Proclamation)
Originally, the noun “proclamation” referred to a formal order publically issued by a legal authority. Later, it acquired a more general use, referring to an authoritative declaration. In the United States, presidents frequently make proclamations, which are either ceremonial or substantive. Notably, without the authorization of Congress, a presidential proclamation is not enforceable by law with the exception of war time and the president’s role as commander in chief. These circumstances allowed Lincoln to circumvent Congress and make this proclamation.