OF GROWTH IN TREES. 103 



Notwithstanding the unbounded liberty which the mind 

 of man seems to possess, it is in reality confined within 

 very narrow limits ; for when we carefully analyze our 

 ideas, simple and complex, we can trace them without an 

 exception to past impressions made on our organization. 

 We can form no conception of anything without a refer- 

 ence to ideas previously acquired by the senses. I may 

 conceive of a golden mountain, but it is obvious that if I 

 had not previously acquired, by impressions from external 

 Nature, the ideas of mountain and gold, it would have been 

 impossible to have formed the combination. 



We are very frequently compelled to receive ideas in- 

 dependently of our will. I may, for instance, be looking 

 out of my window, and see a man shot down, and a year 

 afterwards recollect the circumstance. I have thus invol- 

 untarily acquired an idea. Impressions thus received, 

 when powerful and painful, will recur again and again, 

 and influence our conduct through life. 



Now if our knowledge of an external object was limited 

 to the moment of perception, and was extinguished for- 

 ever with the fading sensation which gave it birth, if we 

 had no memory of past impressions, then we should be 

 creatures utterly incapable of reasoning or reflection. 

 But we are so constituted that the knowledge derived 

 from without lives within us. All our past impressions 

 are secured to us. They are associated together accord- 

 ing to certain laws, which have evidently been contrived 

 with the most admirable adaptation to our wants, so as to 

 bring again the knowledge previously acquired by the 

 senses at the very time when its return is the most profit- 

 able. " A burnt child fears the fire," for example. Hence 

 we are ever expanding ourselves over the long series of our 

 past sensations, for memory is the mind relapsing into a 

 former state, and the use of reason becomes more and 

 more apparent, as these sensations from the external world 

 are increased in number and variety. 



How beautifully are the upper and lower extremities of a 



