* Moral opposition to slavery. Many northerners believed that slavery was morally wrong and that it should be abolished. This belief was often rooted in religious convictions, as many northern Protestants considered slavery to be contrary to Christian teachings. Others opposed slavery on humanitarian grounds, believing that it was cruel and unjust to hold people in bondage.
* Economic self-interest. Some northerners believed that slavery was harmful to the northern economy. They argued that slavery created unfair competition for free labor, driving down wages and making it difficult for northern businesses to compete. Additionally, some northerners believed that slavery prevented the development of a diversified economy in the South, limiting opportunities for trade and investment.
* Political concerns. Some northerners feared that the growing power of the slave states in the federal government threatened the interests of the North. They worried that the spread of slavery would increase the political power of the South and that this would lead to policies that favored the South at the expense of the North. Additionally, some northerners believed that the existence of slavery undermined the ideals of democracy and self-government.
It is important to note that not all northerners supported personal liberty. Many northerners, particularly those who had economic ties to the South, supported the continuation of slavery. Additionally, some northerners simply did not care about the issue of slavery or believed that it was not their concern. However, the arguments in favor of personal liberty were influential in shaping northern public opinion and contributing to the growing opposition to slavery in the North.