The thing is, Jeremy - the SPGB is not any kind of party. It's a cult, the Marxian analogue of the Jehovah's Witnesses. It has an unshakable body of dogma - a particular interpretation of the writings of Marx and Engels - and, just like the JWs, it devotes itself above all to decrying the sinfulness of all the other false Marxists and socialists. To be fair, that is not hard to do, but in adopting this stance - again like the JWs with regard to Christianity - the SPGB has to lose an important part of the essence of Marxism. Because Marx and Engels were materialists, and spent their lives engaging with the real world, working alongside people they only partially agreed with in pursuit of common objectives - reforms! (horror!) - which they considered worthwhile. The SPGB is a thoroughgoing idealist cult, which measures everything against the yardstick of its purist maximalism. And given that no reform, gain or change can possibly come anywhere near the SPGB's fantasy society, all practical activity must be dismissed as pointless. Only preaching the faith and denouncing the false Marxism of the sinners is permissible. Just as the mainstream Christian churches do their practical work - for better or for worse - in their communities while the JWs just carp, so the rest of the socialist and communist movement tries to mobilise and organise - sometimes wisely, sometimes stupidly - while the SPGB just carps. That's its niche in the socialist ecosystem - entirely useless, but a niche nonetheless.