The Four States of Libertas Naturae

libertas naturae - (freedom of nature); "the liberty that is proper to a being given its particular nature." (Muller 176). The four states of libertas naturae are as follows:

a. libertas Adami - (freedom of Adam); "before the fall - this is the ability or power not to sin." (Muller 176).

b. libertas peccatorum - (freedom of sinners); a freedom that is proper to and confined within the limits of fallen nature and is therefore an absolute inability to do good or to act for the good with the sinner described as not able not to sin." (Muller 176).

c. libertas fidelium - (freedom of the faithful); "a freedom of those regenerated by the Holy Spirit that is proper to the regenerate nature and is characterized by the ability to sin and to do good." (Muller 176).

d. libertas gloriae - (freedom of glory); "a freedom proper to the fully redeemed nature of [the blessed in heaven], who, as residents of the heavenly kingdom are now characterized by the inability to sin." (Muller 176).

The four states of man in relation to sin enumerated by Augustine of Hippo: (a) able to sin, able not to sin (posse peccare, posse non peccare); (b) not able not to sin (non posse non peccare); (c) able not to sin (posse non peccare); and (d) unable to sin (non posse peccare). The first state corresponds to the state of man in innocency, before the Fall; the second the state of the natural man after the Fall; the third the state of the regenerate man; and the fourth the glorified man.

For more on this topic:
Human Nature in Its Fourfold State: Thoughts on Augustine's View on the Will.
Libertas Peccatorum - Man's State of Sin After the Fall by Robert J. Olson
The Fall and Imputation of Sin @monergism