Kevin Williamson is wrong in stating no Robert Burns biography explores how the 1783 Laki eruption damaged his health (The ploughman and the volcano, Essay of the week, January 12).

This is central in my 2009 biography, The Stars Of Robert Burns.

My book shows why Robert Burns thought as he did, from his experiences in the 18th century, when science fought with superstition. It extracts strong messages for today.

Dr Catherine Smith

Stirling