What concept is central to Douglas’ argument in this document?

I firmly believe that the authority to determine the future of slavery in these new territories rests not with distant lawmakers but with those who call these lands home. The people in these territories must exercise their own judgment without unwarranted interference from the federal government. Their collective voice shall decide whether to welcome freedom or to maintain the institution of slavery. I assert that this practice of popular decision-making will foster a spirit of self-determination and independence. Let the choice be made by the majority of those directly affected by such monumental issues. In this way, each community may chart its course according to its distinct character and needs.

• Stephen Douglas, Address on Popular Sovereignty, June 1854