This paper considers a Ramsey model of linear taxation for an economy with capital and two kinds of labor. If the government cannot distinguish between the return from capital and the return from entrepreneurial labor, then there will be positive capital income taxation, even in the long run. This happens because the only way to tax entrepreneurial labor is by also taxing capital. Furthermore, under fairly general conditions, the optimal tax on observable labor income is higher than the capital tax, although both are strictly positive. Thus, even though both income taxes are positive, imposing uniform income taxation would lead to additional distortions in the economy.