The main argument of this post is as follows: because who we are is based in part upon our biology and in part upon our environment, and because we are not responsible for our biology nor our initial environment, we are ultimately not responsible for what we do because what we do is based upon who we are.
More formally, the author states that:
...you can’t at any later stage of life hope to acquire true or ultimate moral responsibility for the way you are by trying to change the way you already are as a result of genetic inheritance and previous experience.
Why not? Because both the particular ways in which you try to change yourself, and the amount of success you have when trying to change yourself, will be determined by how you already are as a result of your genetic inheritance and previous experience.
My problem with this reasoning is that we—as Deterministic individuals—exist in an environment with other such individuals. Many of them. Our interactions result in emergent phenomena that cannot be explained by the actions of any one person alone.
Our biology (brains) are affected by our decisions, which would then of course affect our decisions, which in turn affect our brains, and so on. We're a complex, iterative, dynamic feedback system. We don't live in a vacuum; rather we are products of our social environment, society, culture, and so on.
This topic has been bugging me more and more lately in terms of a similar fallacy as arises in neuroscience. Neuroscientists talk about functional localization in the brain as if "functions" are things can be placed on a map. Hell, I just wrote a book chapter about why I think that this is not the right way to talk about these problems. Similarly, philosophers talk about Free Will as though it is a binary either/or.
Free will and brain functioning are active, dynamic processes! It may very well be True that a baby or child cannot be held responsible for its actions; that it is not possessed of Free Will but is driven by genetic and environmental factors; that it is Deterministic. But much like a series of particles placed in an enclosed sphere, if you start with one hundred particles all moving away from one another, away from the center, you can precisely map their locations. But soon their intercollisions become more complicated (chaotic) such that tracking them becomes a computationally exhausting endeavor. Scale that up to a thousand, a million, or a thousand million particles and eventually this problem becomes intractable.
Early in our lives we lack Freedom and Will, and though our initial course may be constrained by genetics and early experience, we can shape our surroundings to alter that course. And though those initial choices may themselves be constrained, as time goes on our end point becomes impossible to trace from our starting condition because of the huge number of options with which we are faced.
We exist in a chaotic environment and there is a symbiotic feedback between our physical brains and our environments that provides a route through which the seemingly non-deterministic aspects of free will might arise.