Can we honestly convince the public and media of the veracity of our passions if we constantly pop up under different campaign banners (one year it's animals, next it's development, then children's rights, then the arms trade)?
There are lots of professional advocates in society, of course - barristers, second-hand car salesmen, media spinners and so on; but campaigners should not see these groups as models. These individuals are paid to promote a specific viewpoint irrespective of their personal beliefs. Campaigners, on the other hand, should believe passionately in what they advocate and have the good fortune to get paid for it. The difference can seem subtle, but it is profound.
Campaigners should absolutely not become guns for hire to be transferred from cause to cause, depending on the salary and benefits package. If we start to get moved around like footballers, we will end up with a huge shortfall in credibility, with our motivations being linked to personal gain rather than passion for the cause we espouse.
All the accusations that our enemies make will be vindicated. Even that old chestnut "you only invent campaigns so you can raise money for them and pay yourself fat salaries" will begin to have some substance.
We might sometimes feel belittled by those in other careers, we may lack benefit packages, professional titles, trade associations, award ceremonies and dedicated TV drama series, but at the end of the day we believe in what we're doing.
A training day organised by King's College London last month is just one of a number of recent initiatives designed to promote campaigning as a career option.
A good deal of this interest is well meant and rightly deplores the lack of training for new campaigners, the ineffectiveness of many campaigns and the need for NGOs to get their act together in terms of advocacy.
However, a reasonable concern about the ability of the third sector to achieve change in society has now matured into a desire to see campaigning as a profession in its own right, with standards and even a career path.
It is here, I think, that a line has been crossed.
Our personal convictions underlie our passion, energy and, ultimately, our credibility as campaigners. It's that unique quality that sets us apart from the mercenaries, and 'professionals'. Whatever you do, don't lose it now. Blake Lee-Harwood is campaigns director of Greenpeace UK