The chart is intended to represent the spectrum, with those doctrines that are least likely to be held by Calvinists at the top, and those least likely to be held by Traditionalists at the bottom, but with incremental steps toward the middle mapped out. As you move toward the middle of the chart, you find more potentially common doctrines. The idea is that you could take a sliding bracket and move up or down the chart, so that you could have eternal security at the bottom of the bracket and Libertarian free will at the top of the bracket, and have a good representation of an actual set of doctrines held by many within the SBC. Additionally, it is illustrated that all of us “slide the bracket” one way or the other to some degree.
The Calvinist doctrine of the perseverance of the saints is often confused with the Baptist doctrine of eternal security (once genuinely saved, always saved), but the two are very different. In fact, the doctrine of perseverance of the saints has much in common with the Arminian doctrine of a losable salvation. Both perseverance and losable salvation portray apostasy as a real and ongoing danger, overcome only by the efforts of the believer in concert with the grace of God. In other words, in the perseverance doctrine, God keep His own by ensuring that their works are sufficient to keep them from falling away; while in the eternal security doctrine, those who genuinely believe in Christ are forever secure based on the works of Christ alone—there is no danger of apostasy.
The term, Traditionalist, is not precisely defined, and covers both non-Augustinians (denying prevenient grace and total inability of the sinner, etc.) as well as those who are more Augustinian (affirming prevenient grace and total inability, etc.).
The distinction between moral inability and natural inability was taught by Jonathan Edwards and Andrew Fuller. A natural inability is like a man born blind, who cannot see no matter how much he might want to. Natural inability provides an excuse. A moral inability is like a rebellious child who holds his hands over his eyes and refuses to see. The inability in both cases is just as debilitating — both will fall into the ditch if they try to walk — but the latter inability provides no excuse.