The 1 - 4 scale was devised by several brilliant minds who grew increasingly frustrated with the inherent subjectivity of rating women on a 1-10 scale of fuckability. Hence, the 1 - 4 scale was created to avoid the dubious, yet frequent dilemma of distinguishing between a "9" an 8.4" a "3.4" etc. The genius of the 1 -4 scale is that it employs a categorical, objective system generally agreed upon by most heterosexual males (and lipstick lesbians, not the butch ones).
Without further ado, here is the breakdown of categories:

A "1": This category is designated for females who you un-mistakenably, undoubtedly, and unabashedly would not have sex with, even in your most inebriated, depressed and lonely state. The "1" is generally characterized by the lethal combination of an ugly face, extreme obesity and very low self-confidence.

The "2":
This category is interesting because a lot more variables come into play here. The "2" is agreed upon to be generally unattractive however due to a variety of circumstances (i.e. shes a butter face, decent face with a fat body, or you have a fetish for 14 year old Malaysian prostitutes), you will have sex with her if you are drunk enough. The key here is that nobody finds out. You make sure you keep this one to yourself.

The "3":
Simultaneously the easiest, yet most problematic category to define. The "3", very broadly put, is a legitimately attractive female who you would unashamedly have sex with. The "3" is worthy o...