The national Presbyterian Church sets standards for the whole denomination. It is local presbyteries, though, which examine and ordain ministers, and even more local sessions (congregational governors) which examine and ordain elders. The locals apply the national standards to individuals. But every individual is a mixture of virtues and vices. No one meets all the national standards perfectly, so every ordination involves judgment about whether a particular person's quirks, even defects, touch any essential tenet of the Reformed faith.
The national standards are not themselves essential tenets. Depending on the locals to rightly sort out how closely the church's officers fit within the essential tenets – without specifying for all times and places what those tenets are – is part of the genius of the American Presbyterian system.
Some people want the national church to define the essential tenets. The church could do this, but it is a long and complicated process. Thus far, in its three centuries in America, the Presbyterian Church has not thought that defining essential tenets was a good idea. It is clear that no one part of the church could define these national standards by itself.
Faced with these obstacles to defining national essential tenets, some people want to do the same thing at the local level. They want presbyteries to draw up lists of essential tenets that they, at least, will use in examining candidates for office.
And this brings us to the interesting point that the first day of discussion of the Peace, Unity, and Purity Task Force report brought out: the locals cannot define local standards of what are the essential tenets. Only the national church can set categorical standards that apply to everyone. The local church must examine each case on its own merit, in relation to those national standards.