We report the demonstration of semi-insulating bulk 4H-SiC without the use of vanadium doping. Single crystal boules were grown by the physical vapor transport method and sliced into wafers. The semi-insulating material was examined with temperature dependent Hall effect, optical admittance spectroscopy, optical absorption and secondary ion mass spectrometry. The material was insulating at room temperature and was not measurable until near 300 degreesC where the resistivity was 4X10(7) Omega . cm. The thermal activation energy is 1.1 eV as determined by temperature dependent Hall effect. Optical admittance spectroscopy detected the 1.1 eV level but did not observe any response in the band around 1.6 eV where the vanadium donor response has previously been detected. Vanadium was below the 10(15) cm(-3) detection limit of our SIMS system. The identity of the defect responsible for the 1.1 eV level has not been identified.