The aim of this paper is to point out the significance of the distinction between liberty and freedom found at certain key points in the works of Adam Ferguson (1723-1816), a prominent Scottish enlightenment thinker in the eighteenth century, and to add a new contribution to the precedent studies. The distinction is important since it shows us that Ferguson develops his understandings of civil liberty by drawing comparison between liberty and freedom. At the core of his thoughts on civil society was "civil liberty" which secures property and rights to all the people under the law. But since civil liberty is fragile, citizens must not blindly obey laws and be always conscious of liberty to maintain it. He argued that civil liberty needs to be reinforced by vigour and freedom as seen significantly in rude people, in order to protect society and its people from despotism. The freedom in rude society was unrestrained one, dependent on rude people's spirit of self-determination. If modern civilized men desire to keep the liberty to choose and pursuit their own objects freely, they must consciously keep rude men's spirit. The active engagement to the society was suggested for this purpose. Thus, civil liberty was conceived as a negative concept by Ferguson, not a positive one. In Ferguson's argument on civil society, rude society and civilized society do not fall into simple dichotomy. Liberty of civilized men and freedom of rude men coexists in the way of the latter reinforcing the former. The message of Ferguson is if we lose the spirit of rude men we would inevitably lose our liberty attained by civilization.