16 
On Some Interactions of Organisms. 
with the facts. The natural presumptions are nearly all 
in their favor. It is also certain that the species best 
worth preserving are the mixed feeders and not those of 
narrowly restricted dietary (parasites, for instance) — 
that while the destruction of the latter would cause in- 
jurious oscillations in the species affected by them, they 
afford a very uncertain safeguard against the rise of 
such oscillations. In fact, their undue increase would be 
finally as dangerous as their diminution. 
Notwithstanding the strong presumption in favor of 
the natural system, when we remember that the purposes 
of man and what, for convenience’s sake, we may call the 
purposes of Nature do not fully harmonize, we find it in- 
credible that, acting intelligently, we should not be able 
to modify existing arrangements to our advantage — 
especially since much of the progress of the race is due 
to such modifications made in the past. 
We should observe, in passing, that the principal gen- 
eral problem of economic biology is that of the discovery 
of the laws of oscillation in plants and animals, and of 
the methods of Nature for its prevention and control. 
For all this, evidently, the first, indispensable reouisite 
is a thorough knowledge of the natural order — an intelli- 
gently conducted natural history survey. Without the 
general knowledge which such a survey would give us, all 
our measures must be empirical, temporary, uncertain, 
and often dangerous. 
Next we must know the nature, extent, and most im- 
portant consequences of the disturbances of this order 
necessarily resulting from human interference — we must 
study the methods by which Nature reduces these dis- 
turbances, and learn how to second her efforts to our own 
best advantage. 
But far the most important general conclusion we have 
reached is a conviction of the general beneficence of 
Nature, a profound respect for the natural order, a belief 
that the part of wisdom is essentially that of practical 
conservatism in dealing with the system of things by 
which we are surrounded. 
