The two opponents in this book, though on opposite sides of the theistic issue, share the rarified atmosphere of academic philosophy, which appears little in touch with down-to-earth understandings in other areas. This while professional philosophers ironically slavishly accept the latest scientific theories, and unsuitably imitate mathematical symbolism in logic. But they assume the aura of standing on higher ground and having greater insights, although philosophy can be held not to have contributed anything to human knowledge since circa the 18th century of British empiricism.
As an example of how philosophers think to know better can serve their "correction" of language. Thus in this book Plantinga repeatedly uses phrases like (p.7) "I'm being appeared to redly" for a customary "I see red". He likely doesn't do the same in ordinary conversation, and whatever the explanation for such phrases, forgotten is that language, including its meaning, is arbitrary and we choose to use it in the most convenient form.
The other author, Tooley, similarly speaks (pp.215-216) of a "widespread systematic error" like observing: "The grass is very green". He says, "when a scientifically educated person looks at green grass now, the belief that the person acquires...will be something like the belief that [the following part of this quotation can be viewed as replacing the quotation that the grass is green] there is a power in the grass to reflect wavelengths of light of such a sort as to produce experiences with the property of qualitative greenness" (notice that while he considers calling the grass green erroneous, he refers to "green grass" in the explanation). As before, whatever the process by which a color is perceived, it is convenient to call the perceived object to be of the color by which perceived.
All knowledge of external reality in fact depends on its appearance to our senses, and we learn this early in life, without elaboration by science. Individual perceptions of objects differ from actual objects, as in their foreshortening under perspective, the objects themselves becoming mental composites of many perceptions. Often we are forced in everyday life to substantiate our initial interpretations--like of perceptions occurring in dim surroundings--making sure they accord with reality.
The weaknesses of the authors extend beyond corresponding pointless prescriptions for language use. It enters their logic in general, a discipline in which philosophers are expected to be expert. I have been for both authors selecting here cases.
Plantinga goes somewhat on a rampage writing (p.54): "how can belief, content, arise from physical interaction among such material entities as neurons?...It's a little like trying to understand what it would be for the number seven, e.g., to weigh five pounds (or for an elephant to be a proposition)...no neuronal event can as such have a content, can be 'about' something". This is related to the centuries-old topic of interaction between mind and body. And it is absurd to deny interaction, a correlation, between the brain and mental content, since it occurs as obviously as any other interaction, regardless of the extent to which particulars are known. I.e., certain events in the brain are 'about' the mental content.
Tooley, no expert, gives a horrendously long "scientific" list of "design faults" in human bodies, a fault-finding the vogue lately in countering "intelligent design". One complaint (p.112) is: "When people become overweight...[then certain potentially helpful] mechanism[s are not] effective and well designed...The result...is enormous suffering because people are overweight--with much overeating resulting from the fact that food can provide comfort when one is under stress". Is my heart to bleed? We are given, beside our bodies, brains and the power of volition, so as to not only depend on the events in our bodies but also on our actions. Overweight is not unavoidable if one works at it--I was a concentration-camp inmate, and there were no overweight fellow-inmates among us.
The book is of course primarily concerned with the existence of God. Plantinga, arguing for it, offers incomprehensible reasons. He somehow wants to convince us that we can abandon the standard ways by which truth is obtained, the use of thorough-going experience and valid inference, and wander off into the imaginary, he several times adducing unconfirmable evidence like Calvin's "Sensus divinitatis" or Aquinas's "internal instigation of the Holy Spirit" (p.153). "Intelligent-design" arguments by non-philosophers fare much better. And Tooley, arguing against the existence of God, persists with a rigid definition of God as an omnipotent, omniscient, and morally perfect being (e.g. p.82), contending it to be the requirement of the major monotheist religions. But a more general concept of a supreme being, referred to as God or Almighty, is expressed by that last designation. Of essential concern is whether there is a like higher power over man, one that possesses whatever further attributes found. This should make the discussed author's insistent attempt to disprove God by evidence of evil irrelevant. A supreme being is as found to be.