Medical Research Council 
MRC Laboratory of Molecular Biology 
University Medical School 
Hills Road, Cambridge, CB2 2QH 
England 
telephone Cambridge ( 0223 ) 4801 1 
telex - 81532 
26th July, 1979 
Dr. William J. Gartland, Jnr., 
Office of Recombinant Activities, 
National Institutes of Health, 
Be the s da, 
Maryland 20205, 
U.S.A. 
Dear Bill, 
I am writing to say that it will not be possible for me to attend 
the meeting of the committee on September 7th. As I mentioned to you 
on the telephone, this would keep me away from Cambridge for too long 
a time and I am afraid that I just cannot alter any of the other plans 
I have made to fit this in. 
There is one point that I would like to emphasise to you: the 
paper I wrote has, as you may realise, a well defined historical context 
in the sense that its aim was to convert as many people as possible to 
an objective and rational method of a priori risk analysis. Essentially 
I argued that where one has no defined knowledge of any particular event 
one has to have a very clear theory on which to base any rational form 
of analysis. This theory must, of necessity, be based on very nearly 
the totality of our biological knowledge and hence the strong emphasis 
on exactly what constitutes natural pathogenesis. It is important to 
recognise that if any of the factors which are used can be assigned zero, 
then everything must be zero for that particular event. Thus if something 
does not express, that is enough; if it expresses and if the product has 
no biological target, that too is enough; and if it expresses and has 
a biological target and cannot gain access to it, that also is of no 
consequence . 
Yours sincerely. 
Sydney Brenner 
