Ivan was my closest colleague for over 30 years. That's not to say that I got to spend a great deal of time with him. He was always involved in too many projects, often with people thousands of miles away, so getting his attention was never easy. But on those occasions when he was focused on something we were doing together, he was like a force of nature. His powers of concentration, his depth and breadth of knowledge, and his creativity in finding unorthodox solutions to knotty problems were simply phenomenal. Just trying to keep up with his reasoning took all of my effort, so my contribution to our many collaborations was primarily to serve as a sounding board -- and to pressure him as well as I could to meet deadlines.

Ivan spent most of his career as a critic of mainstream syntactic theory. This was not a role he relished, but his intellectual standards did not allow him to compromise rigor and consistency to the extent that would have been required for his work to be more widely accepted. Despite his status as an outsider, the power of his ideas made it impossible for mainstream theorists to ignore his research. His work on such topics as ellipsis, questions, coordination, binding, long-distance dependencies, idioms, and the syntax/semantics interface will continue to be influential for decades to come.

Ivan's passing left a hole not only because of his immense intellectual contributions, but also because of his expansive personality. He loved interacting with other people, and people were drawn to him. The residences he organized at linguistics institutes and his band, Dead Tongues, did much to break down barriers between the professional and personal lives of the people in his sphere of influence. If he got to class early, while waiting for the beginning of class, he would look at a student and say, "Tell a joke!" Even if the student couldn't come up with one, the invitation would serve to break down barriers and get students talking.

Having Ivan to interact with for all those years is one of the things that made my career at Stanford a dream job. It hasn't been the same for over four years now, since he started treatments for the cancer that ultimately took his life. But I am very grateful for the years of friendship and working together.