Yes, in many ways, but perhaps most important, synthesis can complement observation, controlled perturbation, and analysis in a science. Technology to enable synthesis has been available to chemists for more than a century, and has contributed to nearly every advance in chemical theory. For example, nearly all of our understanding of the chemical behavior of enzymes, metabolisms, and even diseases has come with the help of chemically synthesized molecules. Synthesis, in turn, allowed chemistry to complete its central paradigms faster than fields lacking synthesis. Fields lacking synthesis include astrophysics, cosmology, and planetary science. Imagine how much faster these fields might advance if we could synthesize new planets, stars or new universes to test their theories. The planet of Magrathea, whose inhabitants, according to The Hitchhiker's Guide to the Galaxy, accumulated fabulous wealth building planets to order, sadly does not exist.
Biology has historically also lacked synthetic technology - at least until the 1970s, with the advent of recombinant DNA technology. At first, biologists used biotechnology to cut and paste single genes, rearranging what was found naturally to modify living systems. In the 1980s, however, synthetic biologists moved away from nature, synthesizing entire genes encoding proteins, generating new artificial genetic systems with extra nucleotide letters, and engineering the expression of proteins with more than 20 different kinds of amino acids. These have already had an impact - for example, 'GACTZP' DNA (DNA built from the natural G, A, C, T nucleotides as well as our synthetic Z and P nucleotides) is, in one of its forms, incorporated into diagnostics assays that measure the load of HIV virions in patients at risk of AIDS. Here, the fact that extra 'letters' in the DNA alphabet do not bind to natural nucleotides allows the clinical assay to detect viral DNA without interference from natural DNA. Today, clinical diagnostics tools based on our synthetic genetic systems help personalize the care of some 400,000 patients annually worldwide. Curious readers will find a 2004 review I wrote on some of these applications listed below.