Why did Abraham Lincoln want to abolish slavery?

Abraham Lincoln always viewed slavery as unjust

Question: Why did Abraham Lincoln want to abolish slavery?
Position1 of 2›: For the people
Argument1 of 2›: Abraham Lincoln always viewed slavery as unjust

Abraham Lincoln viewed slavery as inhumane and unjust from the beginning of his life. His advocacy against slavery led to the passing of the Emancipation Proclamation and the 13, 14, and 15th amendments.

The argument

Abraham Lincoln viewed slavery as morally unjust and wrong from the beginning of his life. Abraham Lincoln worked alongside abolitionists to improve Black lives and abolish slavery. In a three hour speech in 1854, Abraham Lincoln admonished slavery and opposed it legally, socially, and economically. Lincoln avidly opposed slavery for the entirety of his life and took measured steps throughout his time as a lawyer and President to work with abolitionists against the institution of slavery.

Premises

[P1]Abraham Lincoln viewed slavery as morally, legally, socially, and economically unjust throughout his life. [P2] He acted on this conviction by working with abolitionists and publicly denouncing slavery, as in his 1854 speech. [C] Therefore, Lincoln sought to abolish slavery because he consistently believed it was unjust.

Counter-arguments

Abraham Lincoln did not seek to end slavery during his term as President. Abraham Lincoln did not wish to alter the Constitution, which sanctioned slavery.

Rejecting the premises

[Rejecting P1] The record is more mixed than "always": Lincoln repeatedly distinguished opposing slavery's extension from abolishing it where it already existed, wrote to Horace Greeley in 1862 that he would save the Union without freeing a single enslaved person if that were possible, and in the 1858 debates disclaimed support for political and social equality. [Rejecting P2] He did not work alongside the abolitionists but kept his distance from them, and Garrison and Phillips were among his critics; he also supported colonisation proposals into 1862, so the 1854 Peoria speech evidences a moral objection to slavery rather than an abolitionist programme. [Rejecting C] A consistent moral objection does not establish the motive for the acts of 1862–65, which the sibling position attributes to war aims and political calculation — the Emancipation Proclamation was issued as a military measure and reached only territory then in rebellion.