all the atoms that make each of us up — the iron in our blood, the calcium in our bones, the carbon in our brains — were manufactured in red giant st… - Carl Sagan

It seems to me what is called for is an exquisite balance between two conflicting needs: the most skeptical scrutiny of all hypotheses that are served up to us and at the same time a great openness to new ideas. If you are only skeptical, then no new ideas make it through to you. You never learn anything new. You become a crotchety old person convinced that nonsense is ruling the world. (There is, of course, much data to support you.)
On the other hand, if you are open to the point of gullibility and have not an ounce of sceptical sense in you, then you cannot distinguish useful ideas from the worthless ones. If all ideas have equal validity then you are lost, because then, it seems to me, no ideas have any validity at all.

Still, the alien biologist might be excused for lumping together the whole biosphere - all the retroviruses, mantas, foraminifera, mongongo trees, tetanus bacilli, hydras, diatoms, stromatolite-builders, sea slugs, flatworms, gazelles lichens, corals, spirochetes, banyans, cave ticks, least bitters, caracaras, tufted puffins, ragweed pollen, wold spiders, horseshoe crabs, black mambas, monarch butterflies, whiptail lizards, trypanosomes, birds of paradise, electric eels, wild parsnips, arctic terns, fireflies, titis, chrysanthemums, hammerhead sharks, rotifers, wallabies, malarial plasmodia, tapirs, aphids, water moccasins, morning glories, whooping cranes, komodo dragons, periwinkles millipede larvae, angler fish, jellyfish lungfish, yeast, giant redwoods, tardigrades, archaebacteria, sea lilies, lilies of the valley, humans bonobos, squid and humpback whales - as, simply, Earthlife. The arcane distinctions among these swarming variations on a common theme may be left to specialists or graduate students. The pretensions and conceits of this or that species can readily be ignored. There are, after-all, so many worlds about which an extraterrestrial biologist must know. It will be enough if a few salient and generic characteristics of life on yet another obscure planet are noted for the cavernous recesses of the galactic archives.

If you know a thing only qualitatively, you know it no more than vaguely. If you know it quantitatively—grasping some numerical measure that distinguishes it from an infinite number of other possibilities—you are beginning to know it deeply. You comprehend some of its beauty and you gain access to its power in the understanding it provides. Being afraid of quantification is tantamount to disenfranchising yourself, giving up on one of the most potent prospects for understanding and changing the world.