What did Abraham Lincoln argued that the country was weakened by?

Abraham Lincoln argued that the country was weakened by the institution of slavery, which he viewed as morally wrong and a fundamental contradiction to the principles of freedom and equality in the Declaration of Independence. He believed that the division between free and slave states created discord, undermining national unity and democracy. Lincoln contended that allowing slavery to persist threatened the survival of the Union and the ideals upon which the nation was founded. Ultimately, he saw the abolition of slavery as essential for the nation's strength and future.