The use of s-expressions which characterize the syntax of Lisp was initially intended to be an interim measure pending the development of a language employing what McCarthy called "m-expressions".
[6] ALGOL 58, originally to be called IAL for "International Algorithmic Language", was developed jointly by a committee of European and American computer scientists in a meeting in 1958 at ETH Zurich.
ALGOL implementors developed a mechanism they called a thunk, which captured the context of the working parameter, enabling it to be evaluated during execution of the procedure or function.
In 1971 Sussman, Drew McDermott, and Eugene Charniak had developed a system called Micro-Planner which was a partial and somewhat unsatisfactory implementation of Carl Hewitt's ambitious Planner project.
Drew McDermott, and Sussman in 1972 developed the Lisp-based language Conniver, which revised the use of automatic backtracking in Planner which they thought was unproductive.
Pat Hayes remarked: "Their [Sussman and McDermott] solution, to give the user access to the implementation primitives of Planner, is however, something of a retrograde step (what are Conniver's semantics?
They eliminated what they regarded as redundant code and, at that point, discovered that they had written a very small and capable dialect of Lisp.
"We were actually trying to build something complicated and discovered, serendipitously, that we had accidentally designed something that met all our goals but was much simpler than we had intended... we realized that the lambda calculus—a small, simple formalism—could serve as the core of a powerful and expressive programming language.
He has also been critical of aspects of Scheme that derive from the lambda calculus such as reliance on continuation functions and the lack of exceptions.
It had a large impact on the effort that led to the development of its sister-language, Common Lisp, to which Guy Steele was a contributor.