One of the great privileges that I knew during the time that I was involved in student ministry with UCCF: the Christian Unions was being able to spend time with the General Secretary Bob Horn. Bob fell asleep in Jesus just over a year ago after a long struggle with cancer. He was an evangelical statesman, a baptist minister who edited firstly Evangelical Times and then Evangelicals Now.
Bob was humble, gracious, kind, generous, and resolute on gospel truth. One of the things that he learned as a theology student was that the alleged strengths of an opposing theological position could very well be its fundamental weakness. I found that tremendously insightful and helpful when evaluating arguments. Rather than be bowled over by a position it makes you pause, reflect and ask questions.
I think that this resonates with Packer's assessment of the Keswick view of holiness. What promised to be the means of victory over sin and the key to holiness in the Christian life was found to be wanting in exegetical rigour, deficient in realism, and pastorally destructive. The promised victory never came to those who imbibed this teaching.
It also holds good for the positive spin that is put on open theism. Here we no longer have the aloof God, the distant sovereign despot. Instead we have a much more compassionate, close, involved God. But all these alleged pastoral benefits that come with an open theistic view are defective and destructive. They are presented as strengths, in reality they are the gravest weakness of the whole system.
This is another tool for evaluating arguments. It can be used alongside the discarding of rhetoric, which is sometimes no more than the shiny wrapping paper, that also disguises bad arguments and makes them more plausible than they really are.