[DiogenesLamp]

I agree. It is misleading. Lincoln had signed an oath to uphold The Constitution. He was, in the main, concerned with preserving the Union. It was his view that secession was unconstitutional.

As has been pointed out, that is not his view in 1848. That was his view only after secession became personally humiliating to him.

Beyond that, the Declaration of Independence says explicitly that people have a right to leave. The Declaration of Independence created the nation, and asserts a higher power than that of legislators who make man made laws.

[HandyDandy]

You may be confusing the concept of revolution vs the concept of rebellion. The boundary between Mexico and Texas was a work in progress and a wholly different situation in 1848, than the situation that Lincoln addressed in his First Innaugural.

[BroJoeK]

DiogenesLamp: "Beyond that, the Declaration of Independence says explicitly that people have a right to leave."

No actual Founder -- not one -- ever declared that states were free to secede "at pleasure".
All insisted or implied that one or both of two conditions must exist:

1. Mutual consent -- meaning the approval of Congress, or,

2. Oppression or usurpations -- meaning a material breach of compact, in Madison's words, "having the same effect".

Neither condition existed in December 1860, and so by our Founders' original intent, Deep South declarations of secession were illegitimate.

Still, that did not start the Civil War.
War only began after the Confederacy provoked, started & declared war, while sending military aid to pro-Confederates in Missouri.