The dean of computing must be respected by the academic staff and be competent to oversee the use of computers on campus.
Conclusion (therefore)
The dean of computing must be a professor from this university's computer science department.
Evidence
The dean of computing must be respected by the academic staff and be competent to oversee the use of computers on campus.
The only deans whom academics respect are those who hold doctoral degrees.
Only someone who really knows about computers can competently oversee the use of computers on campus.
The board of trustees has decided that the dean of computing must be selected from among this university's staff.
Evaluate
The argument is concluding that the only suitable candidates for dean must come from the university's computer science department, based on the criteria of holding a doctoral degree, being knowledgeable about computers, and being part of the university's staff.
We need to question whether these criteria exclusively apply to professors from the computer science department.
One potential flaw is if there are other staff members at the university who meet both the requirement of holding a doctoral degree and having substantial knowledge about computers, without being from the computer science department. Such a possibility would challenge the necessity of the dean being selected strictly from the computer science department.
Goal
Let's find an answer that shows there could be individuals within the university, not necessarily within the computer science department, who still meet all the necessary criteria for becoming the dean of computing.